TEGEST as promising tool for assessing the risk of perioperative neurocognitive disorders

Abstract

Background

Perioperative neurocognitive disorders are often neglected and undiagnosed. There are known risk factors for these disorders (e.g., higher levels of frailty, cognitive decline before surgery). However, these factors are usually not assessed in the daily clinical setting. One of the main reasons for this lack of examination is the absence of a suitable cognitive function test that can be used in acute clinical settings. The primary aim of this study was to determine correlations between preoperative and postoperative scores on three cognitive tests (the Mini Mental State Exam (MMSE), the Clock Drawing Test (CDT) and the Test of Gestures (TEGEST).

Methods

This was a prospective, monocentric, observational study that included one cohort of patients aged 65 years and older. Patients underwent acute or elective surgical operations. Preanaesthesia tests were administered. After the operation, the patients completed the same tests between the 2nd postoperative day and discharge. Preoperative and postoperative cognitive test scores were assessed.

Results

This study included 164 patients. The arithmetic mean age was 74.5 years. The strongest correlations were observed between MMSE scores and TEGEST scores (r = 0.830 before and 0.786 after surgery, P < 0.001). To compare the MMSE and the TEGEST, the MMSE was divided into 2 categories—normal and impaired—and good agreement was found among 76.2% of the participants (ϰ = 0.515). If the TEGEST scoring system was changed so that scores of 4–6 indicated normal cognition and scores of 0–3 indicated cognitive impairment, the level of agreement would be 90.8%, ϰ = 0.817. Only 5.5% of the patients had impaired MMSE scores and normal TEGEST scores, whereas 3.7% of the respondents normal MMSE scores and impaired TEGEST scores.

Conclusion

According to our results, the TEGEST is a suitable option for assessing cognitive functioning before surgery among patients who are at risk of developing perioperative neurocognitive disorders. This study revealed that it is necessary to change the rating scale for the TEGEST so that scores of 4–6 indicate normal cognition and scores of 0–3 indicate cognitive impairment. In clinical practice, the use of the TEGEST may help to identify patients at risk of perioperative neurocognitive disorders.

Background

In 2018, the Perioperative Cognition Nomenclature Working Group changed the nomenclature of the term “postoperative cognitive dysfunction” [1]. The main recommendation was that the term perioperative neurocognitive disorders (PNDs/NCDs) should be used as an overarching term for cognitive impairment identified in the preoperative or postoperative period [1]. Individuals over 65 years of age have the highest risk of developing PNDs/NCDs [2]. Preoperative cognitive dysfunction is known to be a risk factor for the development of PND [3]. When cognitive dysfunction is established before an operation (even as an indicator), the trajectory of the patient’s perioperative period should change because the patients should be considered to be at risk of PNDs [3]. The consequences of PNDs/NCDs can led to considerable changes for patients. The most severe complications include loss of independence, higher morbidity, and the development of persistent neurocognitive impairment [2]. The onset of PNDs/NCDs is multifactorial and involves predisposing and precipitating factors [4]. According to current knowledge from experts, it is advisable to preoperatively or perioperatively identify patients at risk of developing PNDs/NCDs [2]. Preanaesthesia examinations can help to identify patients at risk of PNDs/NCDs; specifically, higher Clinical Frailty Scale scores, cognitive deficits, and age over 65 years are risk factors for these disorders [2]. However, cognitive tests in preanaesthesia examinations are not routinely performed. One of the many reasons for this may be the lack of a suitable cognitive functioning test that is quick to administer and could be used in everyday practice. Other reasons for not performing these examinations may include insufficient staffing, excessive workloads, and a lack of knowledge regarding the aetiology of PNDs/NCDs [5].

This study aimed to identify a quick test that is suitable for everyday clinical practice. There is currently a lack of commonly used preoperative cognitive assessments among anaesthesiologists in the Czech Republic, thus highlighting the urgent need for rapid and affordable tools. Cognitive assessments can provide early indications of abnormal cognition or even its severity. In potential cases of severe cognitive dysfunction, specialised assessments should be performed by psychiatrists, geriatricians or general practitioners. An evaluation of cognitive function can help to decide whether informed consent could be signed by a patient. Overall, cognitive assessments ultimately lead to higher levels of patient safety, acceptance of patient autonomy, easier communication with families and good clinical practice.

This study aimed to determine whether there was consistency between preoperative and postoperative cognitive function test scores.

Methods

Study design and setting

This prospective, monocentric, observational study included one cohort of patients. The participants were recruited between October 2020 and March 2023, and the final follow-up occurred on 22 November 2023. The respondents had various socioeconomic backgrounds and levels of education. The study took place in the Czech Republic at Tomas Bata Hospital in Zlin (approx. 13,000 general or regional anaesthetics administered in 2022). The respondents underwent elective, semi-elective or acute surgery under general or regional anaesthesia (orthopaedic and traumatological surgeries, general and vascular surgeries, neurosurgeries, gynaecological surgeries, otorhinolaryngological surgeries, urological surgeries, eye surgeries). Preoperative and postoperative testing took place in the anaesthesiology outpatient clinic or in the hospital ward.

Patients who underwent emergency surgery (including those with life-threatening conditions) were excluded from the study due to their potentially lower ability to perform well on cognitive tests.

The data were obtained using three cognitive function tests: the Mini-Mental State Exam (MMSE), the Test of Gestures (TEGEST) and the Clock Drawing Test rated with BaJa scoring. All three tests have been validated in the Czech population [6,7,8]. An unauthorized version of the Czech MMSE was used by the study team without permission, however this has now been rectified with PAR. The MMSE is a copyrighted instrument and may not be used or reproduced in whole or in part, in any form or language, or by any means without written permission of PAR (www.parinc.com).

The Clinical Frailty Scale (version 2, by Rockwood) was used preoperatively to assess patients’ functional reserve.

The respondents were verbally informed about the possibility of cognitive function testing before the start of their preoperative assessment, and they had approximately 15–20 min to decide whether they wanted to participate in the study. Informed consent was obtained from patients prior to the start of the study in accordance with Czech and European regulations for clinical trials. The language barrier was eliminated because patients signed an informed consent form in the Czech language. According to Czech legislation, these forms can only be signed willingly by the patient. Consent had to be free, intelligible, qualified and informed [9]. The doctor who signed the informed consent was responsible for ensuring that these conditions were met.

Before administering the assessments, patients were verbally informed about the process of testing (information about the tests and their order and time frame). The minimum time frames for the assessments were as follows: 12 min for the MMSE, 7 min for the CTD, and 6 min for the TEGEST. If necessary, the time frames were individualised. Respondents were asked about any sensory impairment (hypoacusis, sight impairment) and were asked to use their sensory aids (glasses). The test administrator was a doctor who specialised in anaesthesiology, resuscitation, and intensive care. The same physician examined the patient before and after the surgery. Only two doctors participated in the examination of the patients (the main administrator and the second doctor). These physicians were certified in anaesthesiology, resuscitation and intensive care medicine by the Czech Society of Anaesthesiology and Intensive Care Medicine. The main administrator has been working in the field for 25 years, and the second doctor has been working in the field for 6 years.

The anaesthesiologist who performed the preoperative testing could not administer general or regional anaesthesia to the patient (Ethics Committee requirement) because of possible bias from the anaesthesiologist (decisions about broader or invasive monitoring during anaesthesia, transfer to the ICU after operation because of cognitive dysfunction before the operation and a greater risk of postoperative delirium). The participants were exposed to general or regional anaesthesia; the decision between the two approaches was made during the preanesthesia examination, depending on the type of operation and the preference of the patients. The study design consisted of a descriptive comparison of three cognitive tests before and after surgery.

The study was carried out in accordance with the amended Declaration of Helsinki. The study was approved by two ethics committees (Ethics Committee of Tomas Bata Hospital in Zlin and Ethics Committee of the Olomouc University Hospital and the Faculty of Medicine and Dentistry, Palacky University Olomouc). Both committees approved the study entitled “Postoperative Cognitive Dysfunction as Geriatric Syndrome”. The reference number in Zlin was 2020 − 121, and the date of approval was 6.10.2020. In Olomouc, the reference number was 159/20, and the date of approval was 12.10.2020. The study was registered at clinicaltrials.gov under ID number NCT05648890.

This study was reported in accordance with the STROBE guidelines.

Participants

All participants were assessed by two doctors: the main administrator and the colleague. The decision to ask patients about possible enrolment was made 24 h before the preoperative anaesthesiology exam by evaluating the online organiser of the anaesthesiology outpatient clinic.

The inclusion criteria were as follows: age 65 years or older, absence of sensory impairment (e.g., visual impairment, hearing impairment), legal capacity, signing of informed consent to participate in the study (a number was assigned to the patient to ensure their anonymity), ability to communicate verbally (e.g., absence of tracheostomy), and elective, semi-elective or acute surgery.

If doubts about the patient’s ability to sign the informed consent arose during testing, the patient’s family or a next of kin was contacted. It is possible to use proxy consent in the Czech Republic. In the study, 37 patients with moderate cognitive impairment and 5 patients with severe cognitive impairment according to the MMSE provided consent via proxy. The reason for contacting the family/next of kin was the cognitive function test scores – these patients were not known to have limited legal capacity preoperatively.

The exclusion criteria were as follows: somnolence, sopor, septic shock, Glasgow Coma Scale score of 14 or less, known psychiatric illness (schizophrenia, personality disorder), effect of pharmacological premedication, and use of antipsychotic or analgesic medications. Patients who refused postoperative testing were also excluded from the study. Furthermore, patients were excluded from the study because of refusal to consent to testing, positivity for SARS-CoV-2, development of septic shock or acute respiratory failure, severe postoperative pain (defined as a Numeric Rating Scale score of at least 7), patient distress, or hospital discharge before postoperative testing.

A total of 203 patients were enrolled in the study. Follow-up was performed in the standard ward or in the ICU between postoperative day 2 (mainly because of the possibility that higher doses of opioids after surgery could affect the results) and discharge (the Ethics Committee stated that the patients could not be followed up after discharge).

Variables

The explanatory variables were the pre- and postoperative cognitive function scores and their Clinical Frailty Scale scores (quantitative variables). The intervening variable was anaesthesia (general or regional). The response variable was the change in compatibility of the three cognitive function tests. The outcomes of the cognitive tests were the scores on the MMSE, TEGEST, and CDT before and after the operation. The Clinical Frailty Scale evaluated a patient’s functional capacity before the operation. The potential preoperative confounders included distress and fear, which could affect a patient’s cognitive testing performance. The potential postoperative confounders included pain and opioid treatment.

Measurement

Cognitive function (explanatory variable) was measured by the MMSE, TEGEST and CDT, and frailty was measured by the Clinical Frailty Scale. All patients had their sensory aids available during the examination if needed (e.g., glasses).

The Mini-Mental State Exam (MMSE) is an internationally recognised test and is recommended as the first-line tool for cognitive screening in the Czech Republic among GPs, geriatricians and social workers [6]. The maximum test score is 30. A score of 24–30 points indicates a normal cognitive condition, 21–23 points represents mild cognitive impairment (or mild dementia), 11–20 points indicates moderate cognitive impairment, and a score below 10 indicates severe cognitive impairment.

The Test of Gestures (TEGEST) was developed in the Czech Republic by Ales Bartos. The TEGEST can detect early impairment of episodic memory [7]. It is a rapid examination of episodic memory – it can usually be completed in 2–3 min. Six gestures representing human senses arranged in an imaginary circle are shown to patients by the administrator. Gestures include eating with a spoon (representing taste), stroking the cheek (touch), talking on the phone (hearing), looking through binoculars (sight), smelling a flower (smell), and putting on glasses (relating to sight) [7]. Gestures can be shown or repeated verbally by a patient. Each gesture is worth one point [7].

The Clock Drawing Test (CDT) rated with BaJa scoring (abbreviation of the surnames of the two main authors, “Bartos”, “Janousek”) has a maximum score of five points. It also assesses multiple cognitive functions (executive, sight, memory, and numerical abilities). BaJa scoring is a quantitative assessment of the CDT. The test is scored based on the clock face. One point is assigned if the positions of the numbers is correct on the clock; one point is assigned if the numbers are draw in the correct position; one point is assigned for the correct number of clock hands; one point is assigned if the hour hand is drawn correctly (11); one point is assigned if the minute hand is drawn correctly (10); and one point is assigned if the sizes of the clock hands are correct. A score of 4 points or less indicates potential cognitive impairment [8]. The main advantage of this approach is its fast administration and short testing time. The main disadvantage is the need for aids (e.g., pencil, paper).

The Clinical Frailty Scale has been validated in a previous study [10]. A higher preoperative score on the Clinical Frailty Scale is a significant risk factor for worse postoperative outcomes, including worse functional outcomes after elective noncardiac surgery [2, 11]. The Clinical Frailty Scale in preanaesthesia examination is important for assessing functional fitness and is widely used in clinical practice. The cutoff score for the Clinical Frailty Scale is 5, and patients with higher scores may have a higher risk of developing cognitive impairment or dementia. Patients with lower functional capacity (i.e., higher Clinical Frailty Scale scores) and patients with cognitive impairment have a higher risk of developing health risks (falls, hospitalisation, death). The term “cognitive frailty” is used, but there is no consensus regarding its definition. According to the literature, cognitive frailty is a predictor of increased morbidity and mortality –moreover, the literature indicates that cognitive frailty is a stronger predictor than independent frailty. Assessments of functional fitness should be a routine part of the preoperative examination [12, 13].

Risk of bias

There was a risk of selection bias due to the way in which patients were enrolled in the study during the preanaesthesia examination. The initial indications of cognitive impairment were obtained during the preanaesthesia examination. This information may have caused patients to feel stressed, anxious or worried, thereby influencing the ir subsequent test results. There was a low risk of information bias because all patients were examined by two doctors. These two doctors did not participate in the administration of general or regional anaesthesia. The population was limited to patients undergoing surgery.

Study size

In the post hoc sample size calculation based on the results of the study, the minimum correlation coefficient for correlations between cognitive test scores was assumed to be Rho = 0.4 with a type I error rate α = 0.05 and a test power = 0.9. The minimum sample size under these conditions is 61 respondents. Given the ordinal nature of the data, nonparametric correlations were assumed; therefore, the estimated sample size was increased by 15%. Hence, the minimum sample size was 71 patients.

The data were processed using TIBCO STATISTICA v. 13.4.0.14.

Statistical analysis

Given the ordinal nature of the data, nonparametric analyses were performed. Spearman’s correlation analysis was used to examine correlations between two variables. The variables include scores on the three tests (the MMSE, TEGEST, and CDT). Differences between 2 independent samples were compared using the Mann‒Whitney U test. The median, minimal, maximal, mean, standard deviation of continuous variables were calculated. Cohen’s kappa coefficient was calculated to determine the level of agreement between preoperative and postoperative scores on the TEGEST, CDT and MMSE. All tests were performed at a significance level of 0.05. The statistical analyses were performed using IBM SPSS Statistics for Windows, version 29.0. Armonk, NY: IBM Corp. Participants who were lost to follow-up and patients with missing data were excluded.

Results

Participants

A total of 203 patients participated in the study (flow diagram 1). A total of 322 potential patients were approached, 268 patients were screened, 58 patients were excluded, and 210 patients were deemed suitable for testing. A total of 203 patients agreed to participate in the study, 39 of whom were subsequently excluded (Table 1). Ultimately, this study included 164 patients. The mean age was 74.5 (± 6.6) years. The most common age among participants was 68 years old (24 respondents), followed by 70 and 81 years old (always 20 responders). The median age was 72 years.

Table 1 Patients excluded from the study

Fig. 1

Study size

Descriptive data

After surgery, patients were hospitalised in a standard ward or intensive care unit, depending on the nature and extent of the procedure, the patient clinical status after the operation and their complications. The decision regarding postoperative hospitalisation was made by an anaesthesiologist in consensus with the operating surgeon. All postoperative intensive care units in the hospital were under the Department of Anaesthesiology, Resuscitation, and Intensive Care. Among the 164 analysed patients, 102 were primarily admitted to the intensive care unit after surgery, 88 were still in the ICU when cognitive testing was performed, and 14 were discharged to the standard ward at the time of testing. Most of the surgeries were elective (79%) and performed under general anaesthesia (97%). Acute operations (21%) were mainly performed under general anaesthesia and included vascular surgery, urological surgery and traumatological surgery. Sixty-two patients were admitted to the standard ward, and 7 patients were transferred to the ICU later in the postoperative period due to postoperative complications. The average follow-up time was 3 days after surgery.

Pain was assessed with the Numeric Rating Scale (NRS), which is simple to administer and routinely used in the hospital where the study was conducted. Scores on the NRS range from 0 to 10 points, where 0 is no pain, 1–3 indicates mild pain, 4–6 indicates moderate pain, 7–9 indicates severe pain, and 10 indicates the worst imaginable pain. Patients with severe pain (NRS score of 7 points or more) were excluded from the study.

Outcome data

The outcomes of the cognitive tests were used to divide patients into two groups. Cognitive functions were measured pre- and postoperatively using three tests (the MMSE, TEGEST and CDT).

The descriptive statistics are presented in Table 2, and the correlations between the scores of the three pre- and postoperative cognitive function tests are shown in Table 3. All tests were significantly correlated with one another. The correlation between the MMSE and TEGEST scores was strong (r = 0.830 before surgery and 0.786 after surgery, P < 0.001). The correlations of the CDT with the MMSE and TEGEST were only moderately strong. The values of the correlation coefficient ranged from 0.4 to 0.6.

The individual relationships between the tests before surgery are also shown in the table. Only half of patients with a normal score on the MMSE had a normal TEGEST score. All patients who had MMSE scores indicating cognitive impairment also had TEGEST scores indicating impairment. Only 23% of the patients with normal MMSE and CDT scores had a normal CDT score. 7% of patients with an MMSE score indicating mild impairment had a normal CDT score. All patients with moderate or severe impairment according to the MMSE also had CDT scores indicating impairment.

The relationship between the TEGEST and the CDT before surgery is shown in Table 4. Agreement between the TEGEST and the CDT was observed in 77.4% of patients (shown in italics). The CDT indicated impairment among 17% of the patients, but the TEGEST scores of these patients were normal. In contrast, 5.5% of the patients with TEGEST scores indicating impairment had normal CDT scores. The Cohen kappa coefficient for the CDT and the TEGEST was ϰ = 0.271, which indicated poor agreement.

During the postoperative period, 43% of the patients with a normal MMSE score had a normal TEGEST score. 5% of the patients who had mild impairment according to the MMSE had a normal TEGEST score. All patients with moderate or severe impairment according to the MMSE had TEGEST scores indicating impairment. These data are presented in Table 5.

Only 20% of the patients within the normal MMSE scores had a normal CDT score. 5% of patients with mild impairment according to the MMSE had a normal CDT score. All patients with moderate or severe impairment according to the MMSE had CDT scores indicating impairment.

Table 6 shows the relationship between the TEGEST and the CDT after surgery. There was agreement in 78% of patients (shown in italics). A total of 16.55% of patients had CDT scores indicating impairment and normal TEGEST scores. In contrast, 5.5% of the patients had a normal CDT and TEGEST scores indicating impairment. Cohen’s kappa coefficient for these tests was ϰ = 0.195, which indicated poor agreement.

Table 2 Descriptive statistics

Table 3 Correlations between the MMSE, TEGEST and CDT scores

Table 4 Relationships between the TEGEST and the CDT before surgery cross-tabulation

Table 5 Relationships between MMSE score and the TEGEST after surgery crosstab

Table 6 Relationships between the TEGEST and the CDT after surgery cross-tabulation

Main results

The strongest correlation was observed between the MMSE and the TEGEST. To compare the MMSE and the TEGEST, the MMSE was divided into 2 categories: normal and impaired (see Table 7). 76.2% of the patients (shown in italics) had good agreement, ϰ = 0.515. Only half of the patients with a normal MMSE score also had a normal TEGEST score.

Table 7 Agreement between the MMSE (2 categories) and the TEGEST before surgery cross-tabulation

If the TEGEST score was changed (moderated), with a score of 4–6 indicating normal and a score of 0–3 representing cognitive impairment, then 90.8% of patients showed agreement (see Table 8, patients in italics), ϰ = 0.817. This coefficient indicates excellent agreement. Only 5.5% of the patients had MMSE scores indicating impairment and normal TEGEST scores, whereas 3.7% of the respondents had normal MMSE scores and TEGEST scores indicating impairment.

Table 8 Changes in the TEGEST norm and its relationship with the MMSE score before surgery cross-tabulation

Postoperative measurements were analysed in a similar way. Table 9 shows the relationships between tests when classifying the MMSE score into 2 categories (normal and impaired). Only 71.9% of the patients agreed well, ϰ = 0.419. Only 43% (33 out of 77) of the patients with a normal MMSE score also had a normal TEGEST score. The TEGEST was more rigorous in assessing cognitive functions.

Table 10 shows the results of changing the TEGEST so that scores of 4–6 indicate normal and scores of 0–3 indicate impairment. In this scenario, 90.9% of the patients (shown in italics) showed excellent agreement, ϰ = 0.817. Only 4.9% of the patients had MMSE scores indicating impairment and normal TEGEST scores, whereas 4.3% of the patients had normal MMSE scores and TEGEST scores indicating impairment. Even in the postoperative period, the TEGEST could lead to a more rapid assessment of a patient’s cognitive functioning.

The results of the Mann-Whitney U test to compare the pre- and postoperative values are shown in Table 11. Between preoperational and postoperation, there was a statistically significant decrease in all tested values, P < 0.05.

Table 9 Agreement between the MMSE (2 categories) and the TEGEST after surgery crosstab

Table 10 Changes in the TEGEST norm and its relationship with the MMSE score crosstab

Table 11 Comparison of preoperative and postoperative values using the Mann‒Whitney U test – CDT, MMSE, TEGEST

Other analysis

The correlations between the Clinical Frailty Scale score and cognitive test scores were calculated. The results are shown in Table 12. Spearman’s correlation analysis showed that frailty was significantly correlated with cognitive test scores both before and after surgery. The strongest correlations were observed between frailty and MMSE scores (r = -0.846 before surgery and r = -0.829 after surgery, P < 0.001 for both). There was moderate correlation between frailty and TEGEST scores (r = -0.695 before surgery and r = -0.677 after surgery, P < 0.001 for both). There were also moderate correlations between frailty and CDT scores (r = -0.521 before surgery and r = -0.508 after surgery, P < 0.001 for both). All of the correlation coefficients were negative, indicating that higher (worse) scores on the Clinical Frailty Scale were associated with lower (worse) scores on the cognitive tests.

Table 12 Correlations between the clinical frailty scale and test scores

Discussion

All of the cognitive tests were significantly correlated with one another. The correlation between the MMSE and the TEGEST was strong. The correlation between the CDT and the TEGEST was only moderate. Furthermore, the correlation between the MMSE and the TEGEST was observed in both the preoperative and postoperative periods. On preoperative examination, impaired cognitive function according to the MMSE was associated with impaired cognitive function according to the TEGEST.

In contrast, only 23% of the patients had normal scores on both the CDT and the MMSE. The reasons for this could include fear of surgery alone, anxiety during the preanaesthesia examination, inattention or a prolonged period of cognitive testing and subsequent tiredness. 7% of the patients who had mild impairment according to the MMSE also had a normal CDT score. The same reasons as above could be applied. The CDT was performed as a third test. All patients with moderate or severe impairment according to the MMSE also showed impairment according to the CDT.

The agreement between the TEGEST and CDT results was 77.4%. 17% of patients showed impairment according to the CDT and had a normal TEGEST score, while 5.5% of the patients had a normal CDT score but showed impairment according to the TEGEST. According to Cohen’s kappa coefficient, there was poor agreement between these two tests.

The strongest correlation was observed between the MMSE and the TEGEST postoperatively; only 43% of patients had normal scores on the TEGEST and the MMSE. These results may have been influenced by the use of opioids as part of postoperative analgesia, or patients may have remembered the MMSE test assignments and tasks. Patients in the Czech Republic undergo a preanaesthesia examination shortly before the actual surgery (0–14 days before the procedure). Furthermore, the surgical procedure itself or an unrecognised form of hypoactive postoperative delirium may have contributed to the poorer outcomes. Postoperative delirium screening is not routinely performed in the ICU, which falls under the anaesthesiology and resuscitation department.

5% of patients who showed mild impairment according to the MMSE also had a normal TEGEST score. In the case of moderate/severe impairment, the outcomes were worse in all patients. Only 20% of the patients had normal scores on both the CDT and the MMSE; however, 5% of patients who showed mild impairment according to the MMSE also had normal scores on the CDT, while all patients who showed moderate or severe impairment according to the MMSE also showed impairment on the CDT. Only 78% of the patients showed agreement between the TEGEST and the CDT, and the kappa coefficient indicated that there was poor agreement.

TEGEST scores of 4 or less indicate potential cognitive impairment.

Due to the strong relationship between the TEGEST and the MMSE, we decided to adjust the norm of the TEGEST. If the TEGEST score norm is changed so that scores of 4–6 points indicate normal and scores of 0–3 points indicate impairment, 90.8% of the patients showed agreement, which is an excellent degree of agreement. A similar analysis of the postoperative measurements yielded an agreement of 90.9%. The TEGEST proved to be a suitable substitute for the MMSE in terms of serving as an indicator of cognitive function. It has other advantages that are suitable for acute clinical practice. The TEGEST does not require additional materials (e.g., pencil, paper), and its administration is simple. The main benefit of this approach is the speed of the test; therefore, it could be considered for acute settings. The primary aim of this study was to identify a cognitive function test that could be used for a wider range of patients (i.e., not only for elective surgery) and in acute hospital settings.

A wide range of tests are used to assess cognitive functions preoperatively, including the MMSE, the Montreal-Cognitive Assessment (MoCA) and the Mini-Cog test. Studies usually examine a specific type of surgery (orthopaedics) and focus on patients undergoing elective surgery [13, 14]. Cognitive testing in these studies usually not only identifies cognitive deficits but also identifies risk factors for PNDs/NCDs [14, 15]. A cross-sectional study by Jia et al. published in 2021 compared the MMSE with the MoCA for assessing mild cognitive impairment (middle-aged and older patients). According to Jia, the MoCA is a better indicator of cognitive function because of its lack of a ceiling effect [16]. Similarly, according to a systematic review comparing the accuracy of the MMSE and the MoCA for assessing mild cognitive impairment among patients with Alzheimer’s disease, the MoCA was found to be a superior screening tool [17]. According to these results, the MMSE is not a feasible option for preoperative cognitive function testing.

Gregory and King conducted one of the largest studies, involving over 21,000 patients older than 65. They used two tests – the Short-Blessed Test (SBT) and the Eight-Item Interview to Differentiate Aging and Dementia (AD8) screening test – to assess cognitive functions objectively and subjectively. Due to the large cohort, there was a low correlation between the two tests. The authors suggested that the main reason for this finding was that the tests assessed other domains of cognitive functioning. The AD8 mainly assesses subjective changes in functions in connection with cognitive impairment. The SBT is an objective test of memory, orientation and concentration.

Our study is the first to compare the TEGEST, the MMSE and the CDT. The MMSE is a well-known, internationally used test. We validated the TEGEST based on the MMSE. The main advantages of the TEGEST include its rapid administration (1–2 min) and the fact that gestures can be easily understood worldwide, thus making it a promising tool for preoperative testing.

It can be used for indicative cognitive screening, with the main aim of identifying patients at risk of PNDs/NCDs. When a patient is at risk of PCDs/NCDs, nonpharmacological preventive strategies should be undertaken [18]. The main benefits of the TEGEST include its rapid administration and its standard interpretation. The TEGEST assesses cognitive functioning, especially episodic memory. The aim of evaluating cognitive functioning during the preanaesthesia examination should not be to obtain a detailed diagnosis of cognitive impairment (this would go beyond the expertise of the field of anaesthesiology, resuscitation and intensive care medicine) but instead to perform an indicative assessment of cognitive functions. This approach may identify a patient at risk who should receive more attention in the perioperative period and be given an individualised approach to decrease the risk of PNDs/NCDs. The TEGEST seems to be a possible substitute for complicated tests of cognitive dysfunction.

This study had several limitations. One of the theoretical limitations was the population, as only patients undergoing surgery were included. This was due to patients being enrolled in the study as part of the preanaesthesia examination. The first indication of cognitive impairment was obtained during the preanaesthesia examination. This information may have caused patients to feel stressed, thereby influencing the subsequent test results. The interruption of the study due to the COVID-19 pandemic (from November 2020 to March 2021 and then again from October 2021 to December 2021) is a methodological limitation. During this period, a significant number of patients became ill with COVID-19, and few elective surgeries were performed. Due to epidemiological reasons and to protect patients and staff, the study was suspended during the pandemic (testing could not be ensured without the use of aids; the need to use protective means and face masks could have biased the test results). Another methodological limitation was the influence of patients’ pre- and postoperative conditions. Several factors could have influenced the results of the preoperative cognitive function tests, including the level of education, stress, worry, preoperative distress, presence or absence of a companion (family, next of kin), and Clinical Frailty Scale scores. Postoperative factors that could have influenced the test results included the extent of the procedure, opioid use, inadequately pain treatment, the development of septic shock, internal disorders, postoperative nausea and vomiting, and hospitalisation in a standard ward or intensive care unit.

A substantial proportion of PND cases are still not prevented, and thus, effective prevention and management strategies are needed in daily clinical practice [18]. In the future, strategies to prevent cognitive impairment should be individualised based on the type of procedure, the acuteness and the individual patient. Routine preanaesthesia examinations are necessary to prevent PND.

Conclusion

What practical changes can be made to prevent the incidence of PND among patients aged 65 or older? The change in the nomenclature in 2018 made it possible to start interdisciplinary collaboration (with psychiatrists, neurologists, or gerontologists), which could be seen as a first important step in ensuring the perioperative safety of this population.

One simple step that is transferable to everyday practice is preoperative cognitive testing. This study showed that the TEGEST has the main attributes required by the fields of anaesthesiology, resuscitation and intensive care medicine. This study also revealed that it is necessary to change the rating scale of the TEGEST so that scores of 4–6 indicate normal cognition and scores of 0–3 indicate cognitive impairment. The TEGEST is a promising tool for preoperative cognitive testing, but it is not the only option.

All the tests examined herein were used only for an indicative assessment of cognitive functions before and after surgery. There may be legal consequences (depending on the sources of law in the country) associated with having patients with severe cognitive impairment sign informed consent forms. For such cases, obtaining “proxy consent” is acceptable in the Czech Republic. In such instances, the family or a next of kin is invited to provide consent on behalf of the patient; the anaesthetic and surgical risks are explained to them, and if they agree to the procedure, this must be documented using an informed consent form.