Development, face and content validity of a preoperative functional capacity questionnaire – an observational study

doi:10.21203/rs.3.rs-2996991/v1

Background

functional capacity, defined as the ability of an individual to perform aerobic work, has been shown to have prognostic value in preoperative risk assessment. Greater functional capacity predicts fewer perioperative complications, especially when measured through objective tests, such as the cardiopulmonary exercise test. Nonetheless, objective tests are not widely available, and only a few questionnaires are validated to estimate functional capacity in this setting. Our objective is to describe the development, face, and content validity of a preoperative functional capacity assessment questionnaire that helps identify patients capable of performing 4 or more METs of effort.

Method

This study followed the STROBE Statement guidance for observational studies. Patients undergoing preoperative risk assessment in a tertiary university hospital were submitted to open interviews about physical activities performed in the last month, and answers were compiled and organized in domains (commuting, household activities, efforts at work, leisure time activities) and estimated efforts in METs. The most frequent answers were used to create the first draft of the questionnaire along with the orientations on how to apply it. The questionnaire was presented to experts for adjustments and, finally, to patients undergoing preoperative risk assessment, leading to the creation of a final version.

Results

sixty patients undergoing preoperative risk assessment were submitted to the open interviews. The most frequent answers were about household activities or efforts during commuting. Only 22% of the patients reported being employed, but 92% of those also reported performing activities that required 4 or more METs. Nine physical therapists, one physician, one linguistic expert, and 10 patients were responsible for the face and content validity of the questionnaire. The final version comprised 24 questions: 8 about household activities, 3 about work activities, 5 about leisure time activities, and 8 about commuting.

Conclusions

The preoperative functional capacity questionnaire developed presents face and content validity for its use in the preoperative risk assessment and might increase the accuracy of the preoperative risk prediction.

Preoperative Care

Risk Assessment

Exercise Test

Exercise Tolerance

Surveys and Questionnaires

Functional capacity can be defined as the ability of an individual to perform aerobic work. Usually, when it is estimated, rather than directly measured, it is expressed in metabolic equivalents (METs). Each MET unit represents approximately 3.5 ml O₂/kg/min energy expenditure(1).

Patients’ functional capacity has shown to have prognostic value in specific preoperative risk assessments, especially when using cardiopulmonary exercise testing, which predicts the risk of postoperative complications and mortality, as well as hospital length of stay(2–6). Thus, preoperative risk management guidelines still recommend its estimation through anamnesis and formal questionnaires, such as Duke Activity Status Index (DASI)(7, 8). Preoperative assessment guidelines often suggest that patients with the ability to perform over 4 METs have a smaller risk of postoperative complications(7, 8).

There are several ways of measuring functional capacity – such as ergometric tests and cardiopulmonary exercise tests (CPET), the latter considered the gold standard(9, 10). Despite giving high-value presurgical prognostic information, CPET is an expensive test and, in resource-constrained settings, it is unlikely that CPET will be routinely used anytime soon.

Nevertheless, objective forms of measuring exercise capacity are not always available and increase healthcare costs, thus leading the scientific community to the development of forms to estimate functional capacity, such as field tests(11, 12) and questionnaires(13, 14).

Questionnaires to assess physical activity and functional capacity are used as surrogates for complementary exams. Unfortunately, despite being suggested their use in preoperative risk assessment guidelines, few questionnaires were developed and successfully validated for this purpose (14, 15), some of these have shown a limited ability to predict postoperative complications(14, 15), or have important cultural interpretation issues(14). Moreover, patients might overestimate their functional capacity when asked about their ability to perform activities, especially when facing serious illnesses that might lead to inactivity or accelerate weight loss and sarcopenia(16), such as cancer or the diseases that motivate the planned surgery.

Hence, this study aims to describe the development, face, and content validity of a preoperative functional capacity assessment questionnaire that helps to identify patients with the ability to perform 4 or more METs of effort.

This observational study enrolled patients from a tertiary university hospital undergoing preoperative risk assessment, following the STROBE Statement guidance for observational studies(17).

The questionnaire focused on activities performed by the patients in the past 30 days.

2.1. First step: open interviews with patients

To create a questionnaire, open interviews about physical activities performed by the patients in their routine were carried out. The convenience sample of patients was from an outpatient preoperative assessment setting or surgical wards. To be included in this step of the project, patients should be over 50 years old, undergoing preoperative risk assessment, and able to answer questions without external help. Patients were invited to participate and fill out an informed consent before being submitted to the individual interview.

Patients were submitted to one open-ended question about physical activities performed in their routine, and one closed-ended question about the most intense physical effort performed in the last two weeks (Fig. 1). Patients’ closed-ended answers about the greatest effort were added in an attempt to help patients remember activities not mentioned previously.

All interviews were recorded, and answers were compiled and organized in physical activity domains (commuting, household activities, efforts at work, leisure time activities) and in estimated METs, according to the 2011 Ainsworth physical activity compendium(18).

2.2. Second step: questionnaire draft creation

The most frequent answers were extracted and used as guides to the creation of the draft of the questionnaire.

Trying to minimize patients’ overestimation of physical capacity, the questionnaire focused on asking if the patient performed each activity in the last 30 days.

Orientation on how to apply the questionnaire was created, to standardize the explanations to patients during the interviews.

2.3. Third step: validation with experts

Face validity refers to adjusting the measurement scale based on how the patients and other users of the test perceive it, aiming to increase the chance that it actually measures what it wants(19).

From May to June 2019, the first draft of the questionnaire, along with the orientation on how to apply it, was presented to: 9 physical therapists, which were postgraduate students or Ph.D., members of a research group focused on the impact of physical activity on systemic diseases; one physician, Ph.D. and perioperative medicine expert; and one linguistic expert. The experts had a mean experience time of 14 years.

Each expert was interviewed separately and asked to give suggestions regarding orientation on how to apply the questionnaire, as well as opinions about the extension and comprehensiveness of the questionnaire, clarity of understanding of each question (and suggestions of how to change each of them, if necessary), and the necessity of inclusion of more questions or to remove repetitive or unnecessary questions. The most frequent comments, opinions, and suggestions were used to reshape the questionnaire.

After all the suggestions from experts and proper adjustments to the questionnaire were made, the second draft was presented to a linguistics expert, which made new suggestions for sentence formulation to improve patient understanding. New adjustments led to a third draft of the questionnaire.

2.4. Fourth step: validation with patients and creation of the final version of the questionnaire.

Patients undergoing preoperative risk assessment were invited to answer the third draft of the questionnaire, as well as give explanations on how they understood each question and if they’d suggest a different form to ask for the same information.

Notes were taken on each answer, suggestion, and interpretation that patients gave for every question asked. Whenever patients' comments were vague, new questions were asked to clarify if the understanding were adequate (Examples in Fig. 3).

The questions had their final adjustment using the suggestions from the patients. Depending on the answers given, questions could be reformulated or removed from the questionnaire. A final questionnaire was created after this step, to be used for a future construct validity study.

2.5. Data Analysis

Patients' characteristics were presented as frequencies for categorical data and mean (± standard deviation) for continuous variables. The sample size was reached by convenience when new interviews with patients added little or no information to that previously recorded.

No statistical inferences were made with the data.

3.1 First step: open interviews

From May to October 2018, sixty patients were submitted to the open interviews: twenty-four (40%) from the outpatient clinic and 36 (60%) from surgical wards. Most patients had 5 to 10 years of education and had a major surgery planned. The patients' main characteristics and comorbidities are described in Table 1.

Table 1: Characteristics of patients included in the open interviews step:

Characteristics

Sex*

Female

38 (63%)

Age**

64 (± 9.5)

Years of education*

4 years or less

5 to 10 years

11 years or more

Unknown

1 (2%)

41 (68%)

9 (15%)

Inpatient assessment*

35 (58%)

Planned procedure*

Major surgery

Minor Surgery

33 (55%)

27 (45%)

Type of procedure*

Open abdominal

Ophthalmologic

Esophageal

Urologic

Abdominal endoscopic

Other

22 (37%)

11 (18%)

9 (15%)

6 (10%)

5 (8%)

7 (12%)

Revised Cardiac Risk Index (RCRI) *

0

1

2

≥3

19 (32%)

25 (42%)

12 (20%)

4 (7%)

Comorbidities *

Hypertension

Diabetes

BMI> 30kg/m²

Coronary disease

Heart failure

Previous stroke/ TIA

Creatinine >2mg/dl

40 (67%)

16 (27%)

6 (10%)

4 (7%)

2 (3%)

5 (8%)

Tobacco use*:

Ever-users

21 (35%)

* Frequency (%)

** Mean (± standard deviation)

TIA: transient ischemic attack

Forty-five patients (75%) reported walking upstairs (4METs), while 19 (32%) also walked upstairs carrying some weight, such as bags, groceries, or even heavier objects (5-8 METs).

Forty patients (67%) reported commuting activities with estimated efforts greater than 4 METs, such as walking uphill, carrying objects while walking, and jogging (4 – 9METs).

Thirteen patients (22%) reported being employed, while 9 (15%) reported labor activities that required 4 or more METs of effort. Nonetheless, 12 of those 13 patients employed, mentioned performing some activity in their routine that required 4 or more METs of effort.

Fourteen patients (23%) reported exercising in their leisure time, with efforts estimated at 2.8 to 9METs. All of them reported performing some activity in their routine with an estimated effort of 4 or more METs.

The most frequent answer domains, as well as respective estimated efforts in METs, are reported in Table 2.

Table 2: Physical activities reported in the open interviews

Physical activity domains	Frequency (%)	Estimated METs
Commuting: - Walking - Stair climbing	56 (93%) 52 (87%) 45 (75%)	2.8 - 5.3 4.0 - 8.8
Household activities - Light - Heavy	53 (88%) 53 (88%) 23 (38%)	2.0 - 3.5 5.8 - 9.0
Efforts at work	13 (22%)	2.5 - 9.0
Leisure time activities	14 (23%)	2.8 - 9.0

Data expressed as frequency (%) over a total of 60 patients interviewed.

METs: metabolic equivalents.

3.1.1 The greatest effort in the last two weeks

While the closed-ended question intended to increase the sensitivity of the interviews to detect activities that required 4 or more METs of effort, only 12 patients (20%) informed different activities from the previously reported ones. Eight patients (13%) informed lighter effort activities than in the open-ended question, whereas only 4 (7%) reported different activities with greater estimated effort.

Most of the answers (70%) were either related to walking (for instance: “walking slowly on level ground, walking uphill carrying objects, walking for exercise) or to stair climbing (such as “stair climbing at a slow pace” or “carrying groceries upstairs”). The frequency of answers in each physical activity domain is described in Table 3.

Table 3 – Greatest effort performed in the last two weeks

Physical activity domains	Frequency (%)	Estimated METs
Commuting: - Walking - Stair climbing	41 (68%) 21 (35%) 20 (33%)	2.8 - 5.3 4.0 - 8.8
Household activities - Light - Heavy	7 (12%) 4 (7%) 3 (5%)	2.5 - 3.8 5.0 - 6.5
Efforts at work	7 (12%)	2.5 - 8.0
Leisure time activities	5 (8%)	3.5 - 8.3

Data expressed as frequency (%) over a total of 60 patients interviewed.

METs: metabolic equivalents.

3.2 Second step: questionnaire draft creation

Using the most frequent answers to the interviews, the first draft of the questionnaire was created in November 2018, organizing the questions into four domains: commuting, household activities, efforts at work, and leisure time activities. Within each domain, questions were presented in order from the smallest to the largest estimated effort.

As it was noted that most of the patients that reported having a job also reported performing activities that were estimated to demand more than 4 METs of effort, it was included the question: “Do you have any professional activities?”. Likewise, all the patients that reported exercising in their leisure time also reported performing activities that demanded more than 4 METs, so the question: “Do you exercise during your leisure time?” was also added.

At this point, the questionnaire comprised: 8 questions about household activities, 4 questions about work activities, 6 questions about leisure time activities, and 8 questions about efforts during commuting.

A brief guide on how to apply the questionnaire was created, trying to minimize observer and information bias(20).

3.3 Third step: validation with experts

All experts were asked if the questions should be organized in a progressive sequence based on effort intensity or based on physical activity domains. Four suggested the sequence should be based on the physical activity domains, while one suggested following the physical activity intensity and the rest believed the sequence wouldn’t be so important. The sequence adopted in the final questionnaire was based on the physical activity domains.

The linguistic expert's focus was on giving suggestions regarding understanding and clarity of the questions and orientation on how to apply the questionnaire. One of the orientations was: “Try to answer the questions in the way you understand them”. She suggested modifying this orientation to: “Ask me if you don’t understand any of the questions”. Nonetheless, this could lead to variations of the explanations made by the researchers applying the questionnaire and, thus, increase the risk of observer and information bias(20). This suggestion was not followed and the original orientation was maintained. Other suggestions given were used, most regarding sentence reformulation or the use of specific words to improve understanding of the questions.

Figure 2 shows an example of the approach used during the experts’ interviews.

3.4 Fourth step: validation with patients and development of the final version of the questionnaire

Ten patients were interviewed while awaiting a preoperative risk assessment consultation at the outpatient clinic. Unlike the interviews with the experts, the patients were asked to answer each question and try to explain what they understood from them, by rephrasing or asking probes. (Example in Figure 3)

After the interviews, one question was removed: “Do you usually get physically tired with your work?”. The question aimed to understand if the patients had a high energy expenditure during their labor activities, but most of the answers didn´t correlate to the intensity of their work. For instance, one patient had a high energy expenditure in his profession using heavy tools, but answered “no” to the question and explained that he was used to his work and didn’t feel so tired. On the other hand, other patients answered “yes”, but did not perform any high-intensity activity at work.

New adjustments were made to the questionnaire and a final version was created in June 2019, now comprising 8 questions about household activities, 3 questions about work activities, 5 questions about leisure time activities, and 8 questions about efforts during commuting (appendix).

This study shows the development and initial validation of a functional capacity assessment questionnaire for patients undergoing preoperative risk evaluation in a tertiary public university hospital.

Sixty patients undergoing preoperative risk assessment in the outpatient clinic or surgical wards were submitted to an interview about physical activity.

Most of these patients had a Revised Cardiac Risk Index of 1 or more (68%), had 5 to 10 years of education (68%), and would be submitted to major surgery (55%). Using patients from the real preoperative scenario is important due to some specificities in this population: most of the high-risk patients are older than the patients included in previous physical capacity questionnaires validation studies, such as the International Physical Activity Questionnaire (IPAQ) and Duke Activity Status Index (DASI)(21)(22); less frequently employed than the report from IPAQ, where 73% of the patients included reported having a professional activity, in comparison with 22% of the patients included in this study; have physical limitations often associated with the surgical pathology, and might overestimate their physical capacity in a context that might lead them through a process of weight loss and sarcopenia(16).

The data from the open interviews lead to possible important information regarding preoperative physical activity fitness estimation, as 92% of those who were employed also reported performing activities that required 4 or more METs in the last month. Likewise, all patients that stated some form of exercise during leisure time also reported performing physical activities with estimated efforts of 4 or more METs. These could be population-specific data, as 63% of the individuals included were elderly patients (60 years or more), and 78% were unemployed or retired.

The most frequent physical activity domains present in patients’ answers were commuting (93%) and household activities (88%). As the ability to perform activities of 4 or more METs are of special importance for the preoperative risk assessment, it is noticeable that 75% of all patients reported climbing stairs in the last 30 days, with estimated efforts of 4.0 to 8.8 METs. This reinforces the importance of stair climbing in estimating physical capacity, as proposed in a previous study in which patients who reported being able to climb 2 flights of stairs had less risk of postoperative complications(15), in addition to a cohort of patients that showed the inability to climb 2 flights of stairs in a symptom-limited stair climbing test was associated with a significantly higher risk of developing postoperative complications(11).

The inclusion of a closed-ended question about the greatest effort performed meant to increase the sensitivity of the interviews to detect physical activities with estimated efforts of 4 or more METs. Nonetheless, only 7% of the interviewed reported some physical activity with higher estimated effort in comparison to those previously stated in the open interview. This way, the question didn’t add much information to the anamnesis recorded.

The validation of the content with experts in physical activity and perioperative medicine increased the chances that important questions would be added or adjusted in the questionnaire, while the participation of a linguistic expert, as well as the validation with patients, was vital to guarantee a clear understanding of the questions.

This study has several limitations. First of all, no sample size for the interview was previously calculated, due to the qualitative nature of the information. Nevertheless, the recruitment continued until the data provided was saturated. Moreover, the population included in the study has some specificities, that may limit generalizability: patients were recruited exclusively in a large public tertiary academic hospital, which may lead to an increased risk of referral bias(23). Still, in the preoperative risk assessment, this is the population with the highest risk of complications and, thus, that needs research the most. Additionally, our study is limited to the development, face validity, and content validity of the questionnaire. The construct validity, with the comparison of the results of the questionnaires against the stair climbing test and the cardiopulmonary exercise testing, is in progress.

Our study also has several strengths. Patients included in the interviews were from surgical wards and outpatient settings, trying to maximize the representativeness of patients undergoing preoperative risk assessment in two different scenarios. Despite being recruited solely from a public academic hospital, developing a questionnaire with this population, instead of using a previously validated questionnaire with so many cultural and language differences(14), might increase the accuracy in predicting patients´ functional capacity in this context. Also, the creation of guidance on how to apply the questionnaire might decrease the risk of information and observer bias.

Some preoperative risk assessment guidelines(24) question the role of self-reported functional capacity assessment, due to conflicting evidence and a lack of studies supporting the evidence. It is noticeable that questionnaires are prone to a series of risks of bias, such as social desirability(25), acquiescence bias(19), or recall bias(26). Nevertheless, using a questionnaire adapted and validated to a population, with a standardized protocol for interviewers might minimize those risks of biases and lead to more accurate answers.

The preoperative functional capacity questionnaire developed presents face and content validity for its use in the prediction of functional capacity during the preoperative risk assessment and might increase the accuracy of the preoperative risk prediction.

The construct validity of the questionnaire, comparing its performance with an objective test, will help in choosing the questions with higher accuracy to predict good functional capacity and will be important to the understanding of the threatened role of self-reported functional capacity in the prediction of postoperative complications.

METs

metabolic equivalents

DASI

Duke Activity Status Index

CPET

cardiopulmonary exercise test

Ethics approval and consent to participate

The study was approved by the hospital Ethics Committee (CAPPesq 3236941), following the Helsinki Declaration.

Consent for publication

Not applicable.

Availability of data and materials

No datasets were used for inferential statistics in this study. For additional information or details about patient interviews, please contact the corresponding author.

Competing interests

The authors declare that they have no competing interests.

Funding

The study authors were responsible for study costs, with no additional funding source involved.

Authors’ contributions

All authors have contributed to the development of this manuscript and approved the manuscript for submission. Lauterbach GP conceived and designed the study, collected the data, interpreted the study findings, discussed the results, and wrote the manuscript. Lunardi AC contributed to the study design, analysis of study findings, manuscript writing, editing, and review of the manuscript. Carvalho CRF contributed to the study design, supervision of data collection, manuscript writing, and review of the manuscript. Martins MA supervised and contributed to the study conception and study design, supervised the data collection, interpretation of study findings, and review of the manuscript.

Acknowledgments

We thank the LIFFE research group physical therapists for the valuable insights given during the face validity of the questionnaire.

Authors’ information

Gerhard da Paz Lauterbach is an Internal Medicine expert and coordinates the perioperative assessment clinic at Hospital Universitário of the Universidade Federal de São Carlos, in São Carlos, state of São Paulo, Brazil.

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No competing interests reported.

Gerhardperioperativemedicinesupplementarymaterial.docx

Development, face and content validity of a preoperative functional capacity questionnaire – an observational study

Status:

Version 1

Abstract

Background

Method

Results

Conclusions

Figures

1. Background

2. Methods

2.1. First step: open interviews with patients

2.2. Second step: questionnaire draft creation

2.3. Third step: validation with experts

2.4. Fourth step: validation with patients and creation of the final version of the questionnaire.

2.5. Data Analysis

3. Results

4. Discussion

5. Conclusions

Abbreviations

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1