Screening for depression: Rasch analysis of the structural validity of the PHQ-9 in acutely injured trauma survivors

Comparing psychopathological symptoms, life satisfaction, and personality traits between the WHO and APA frameworks of gaming disorder symptoms: A psychometric investigation

INTRODUCTION

The inclusion of Internet Gaming Disorder (IGD) in the fifth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) by the American Psychiatric Association and Gaming Disorder in the 11th revision of the International Classification of Diseases (ICD-11) by the World Health Organization requires consistent psychological measures for reliable estimates. The current study aimed to investigate the psychometric properties of the Gaming Disorder Test (GDT), the Ten-Item Internet Gaming Disorder Test (IGDT-10), and the Five-Item Gaming Disorder Test (GDT-5) and to compare the WHO and the APA frameworks of gaming disorder symptoms in terms of psychopathological symptoms, life satisfaction, and personality traits.

METHODS

A sample of 723 Swedish gamers was recruited (29.8% women, 68.3% men, 1.9% other, Mage = 29.50 years, SD = 8.91).

RESULTS

The results indicated notable differences regarding the estimated possible risk groups between the two frameworks. However, the association between gaming disorder symptoms and personality traits, life satisfaction, and psychopathological symptoms appeared consistent across the two frameworks. The results showed excellent psychometric properties in support of the one-factor model of the GDT, IGDT-10, and GDT-5, including good reliability estimates (McDonald's omega) and evidence of construct validity. Additionally, the results demonstrated full gender and age measurement invariance of the GDT, IGDT-10, and GDT-5, indicating that gaming disorder symptoms are measured equally across the subgroups.

CONCLUSION

These findings demonstrate that the IGDT-10, GDT-5, and GDT are appropriate measures for assessing gaming disorder symptoms and facilitating future research in Sweden.

The Cyborg Method: A Method to Identify Fraudulent Responses from Crowdsourced Data

Crowdsourcing is an essential data collection method for psychological research. Concerns about the validity and quality of crowdsourced data persist, however. A recent documented increase in the number of invalid responses within crowdsourced data has highlighted the need for quality control measures. Although a number of approaches are recommended, few have been empirically evaluated. The present study evaluated a Cyborg Method that used automated evaluation of participant meta-data and a review of short answer responses. Two samples were recruited - in the first, the Cyborg Method was applied after data collection to gauge the extent to which invalid responses were collected when a priori quality controls were absent. In the second, the Cyborg Method was applied during data collection to determine if the method would proactively screen invalid responses. Results suggested that Cyborg Method identified a substantial portion of invalid responses and both automated and human evaluation components was necessary. Furthermore, the Cyborg Method could be applied proactively to screen invalid responses and substantially reduced the per participant cost of data collection. These results suggest that the Cyborg Method is a promising means by which to collect high quality crowdsourced data.

Early vocational rehabilitation and psychological support for trauma patients to improve return to work (the ROWTATE trial): study protocol for an individually randomised controlled multicentre pragmatic trial

BACKGROUND

Moderately severe or major trauma (injury severity score (ISS) > 8) is common, often resulting in physical and psychological problems and leading to difficulties in returning to work. Vocational rehabilitation (VR) can improve return to work/education in some injuries (e.g. traumatic brain and spinal cord injury), but evidence is lacking for other moderately severe or major trauma.

METHODS

ROWTATE is an individually randomised controlled multicentre pragmatic trial of early VR and psychological support in trauma patients. It includes an internal pilot, economic evaluation, a process evaluation and an implementation study. Participants will be screened for eligibility and recruited within 12 weeks of admission to eight major trauma centres in England. A total of 722 participants with ISS > 8 will be randomised 1:1 to VR and psychological support (where needed, following psychological screening) plus usual care or to usual care alone. The ROWTATE VR intervention will be provided within 2 weeks of study recruitment by occupational therapists and where needed, by clinical psychologists. It will be individually tailored and provided for ≤ 12 months, dependent on participant need. Baseline assessment will collect data on demographics, injury details, work/education status, cognitive impairment, anxiety, depression, post-traumatic distress, disability, recovery expectations, financial stress and health-related quality of life. Participants will be followed up by postal/telephone/online questionnaires at 3, 6 and 12 months post-randomisation. The primary objective is to establish whether the ROWTATE VR intervention plus usual care is more effective than usual care alone for improving participants' self-reported return to work/education for at least 80% of pre-injury hours at 12 months post-randomisation. Secondary outcomes include other work outcomes (e.g. hours of work/education, time to return to work/education, sickness absence), depression, anxiety, post-traumatic distress, work self-efficacy, financial stress, purpose in life, health-related quality of life and healthcare/personal resource use. The process evaluation and implementation study will be described elsewhere.

DISCUSSION

This trial will provide robust evidence regarding a VR intervention for a major trauma population. Evidence of a clinically and cost-effective VR intervention will be important for commissioners and providers to enable adoption of VR services for this large and important group of patients within the NHS.

TRIAL REGISTRATION

ISRCTN: 43115471. Registered 27/07/2021.

Establishing the measurement precision of the patient health questionnaire in an adolescent sample

BACKGROUND

Technically sound measures are necessary for accurately identifying youth at risk for depression, but many studies rely on classical test theory metrics or adult samples to evaluate measures. This study examined the use of the PHQ-8, a common and freely available pediatric depression screener, in an adolescent sample using item response theory (IRT).

METHODS

Secondary analyses were conducted on data from a study conducted in Midwestern middle schools in which 1224 youth completed the PHQ-8 as part of a battery of surveys. Polytomous IRT analyses (a Graded Response Model) were used to evaluate the PHQ-8. Items were examined for their ability to distinguish between respondents of different latent depression severity and for differential item functioning (DIF) across demographic categories.

RESULTS

All PHQ-8 items had adequate discriminative abilities. Items measuring anhedonia and psychomotor disturbances performed relatively poorly, and items measuring somatic symptoms (appetite and sleep) were most informative when respondents endorsed extreme response options ("not at all" or "nearly every day"). No DIF was found across grade level or race, but several items were flagged for DIF by gender and student income level.

LIMITATIONS

These results might not be generalizable to a broader youth population due to administration setting and the unique demographic characteristics of this sample (76.0 % African American).

CONCLUSIONS

Tools such as the PHQ-8 are appropriate to quickly screen for depression in adolescents, but further scrutiny of adolescent response patterns is warranted. Future research should examine items measuring anhedonia and psychomotor and somatic disturbances in adolescents.

Rasch analysis of the beck depression inventory in a homeless and precariously housed sample

The approach to analysis of and interpretation of findings from the Beck Depression Inventory (BDI), a self-report questionnaire, depends on sample characteristics. To extend work using conventional BDI scoring, the BDI's suitability in assessing symptom severity in a homeless and precariously housed sample was examined using Rasch analysis. Participants (n=478) recruited from an impoverished neighbourhood in Vancouver, Canada, completed the BDI. Rasch analysis using the partial credit model was done, and the structural validity, unidimensionality, and reliability of the BDI were studied. A receiver operating characteristic curve determined a Rasch cut-off score consistent with clinical depression, and Rasch scores were correlated with raw scores. Good fit to the Rasch model was observed after rescoring all items and removing Item 19 (Weight Loss), and unidimensionality and reliability were satisfactory. Item 9 (Suicidal Wishes) represented the most severe symptom. Rasch-based scores detected clinical depression with moderate sensitivity and specificity, and were positively correlated with conventional scores. The BDI in a community-based sample of homeless and precariously housed adults satisfied Rasch model expectations in a 20-item format, and is suitable for assessing symptom severity. Future research on depression in similar samples may reveal more information on using specific symptoms to determine clinical significance.

Comparing the construct validity of the Patient Health Questionnaire (PHQ-9) and the Major Depression Inventory (MDI) using Rasch analysis

OBJECTIVE

The Patient Health Questionnaire (PHQ-9) and the Major Depression Inventory (MDI) are psychometric instruments frequently used for depression diagnosis and monitoring in primary care settings. The goal of this study was to assess and compare the construct validity of the PHQ-9 and the MDI using Rasch analysis.

METHODS

The PHQ-9 and the MDI were distributed in random ordering (first or last) to a waiting room sample of Danish primary care patients. Analysis of fit to the Rasch model, ordering of response categories, dimensionality-testing, test for differential item functioning, test for local dependency, and calculation of reliability indices were used to evaluate the psychometric characteristics of the instruments.

RESULTS

A sample of 281 persons (18-87 years, 72 % females) responded to both instruments. Reliability was acceptable for PHQ-9 (PSI 0.80) and excellent for MDI (PSI 0.88). Both instruments demonstrated fit to the Rasch model after rescoring of all items. Dimensionality testing supports that both instruments are unidimensional. Indication of local dependency was observed for PHQ-9 item 2&6 and MDI item 1&4. No indication of differential item functioning regarding age, gender or ordering of instruments was found.

CONCLUSION

The PHQ-9 and the MDI both demonstrate measurement problems. Modifying individual items and reducing the number of response categories in both instruments could potentially improve their measurement capabilities. Study findings do not provide a conclusive indication of which instrument has superior operating characteristics.

The Hopkins Symptom Checklist (SCL-90-R): A Patient-Reported Outcome Measure in Parkinson's Disease

Objective: This is the first study applying Clinimetric Patient-Reported Outcome Measures (CLIPROM) criteria to evaluate the construct validity, sensitivity, and clinical utility of the SCL-90-R in patients with Parkinson's disease (PD). Methods: A Rasch analysis was conducted using a sample of 488 PD outpatients. Results: Testing for dimensionality revealed that less than 5% of t-tests were significant, indicating that the SCL-90-R subscales entailed the property of construct validity. As to the total score, a Person Separation Reliability Index of .96 was found. Conclusions: The SCL-90-R total score is a sensitive screening measure that can be used not only to differentiate healthy stress reactions from symptoms of psychological distress but also to detect PD patients with an increased risk for psychiatric complications. As to the subscales, the brief versions that did not include misfitting items should be used to assess the severity of specific symptoms of psychological distress affecting PD patients.

Cross-cultural validity of the WHO-5 Well-Being Index and Euthymia Scale: A clinimetric analysis

BACKGROUND

The assessment of psychological well-being and euthymia represents an emerging issue in clinical psychology and psychiatry. Rating scales and indices such as the 5-item version of the World Health Organization Well-Being Index (WHO-5) and the Euthymia Scale (ES) were developed but insufficient attention has been devoted to the evaluation of their cross-cultural validity. This is the first study using Clinimetric Patient-Reported Outcome Measures (CLIPROM) criteria to assess cross-cultural validity and sensitivity of five different versions of the WHO-5 and ES.

METHODS

A multicenter cross-sectional study involving a total of 3762 adult participants from different European (i.e., Italy, Poland, Denmark) and non-European (i.e., China, Japan) countries was conducted. Item Response Theory models (Mokken and Rasch analyses) were applied.

RESULTS

Mokken coefficients of scalability were found to range from 0.42 to 0.84. The majority of the versions of the WHO-5 fitted the Rasch model expectations. Paired t-tests revealed that the Italian and Danish WHO-5 versions were unidimensional. Person Separation Reliability indices showed that the Polish, Danish, and Japanese ES versions could reliably discriminate between subjects with different levels of euthymia.

LIMITATIONS

A convenience sampling was used, thus limiting the generalizability of study findings. In addition, no measures of negative mental health were administered.

CONCLUSIONS

WHO-5 can be used in international studies for cross-cultural comparisons since it covers transcultural components of subjective well-being. Findings also suggest that the ES can be used as a cross-cultural screening tool since it entailed the clinimetric property of sensitivity.

Developing and Validating the Narcissistic Personality Scale (NPS) among Older Thai Adults Using Rasch Analysis

Background: Being older could be stressful, especially among people with narcissistic personality disorders. Nevertheless, the tool is yet to be available among older Thai individuals. The study aimed to develop a tool to detect symptoms of narcissistic personality, and to validate its psychometric properties among older Thai adults. Methods: The Narcissistic Personality Scale (NPS) was developed based on nine domain symptoms of narcissistic personality disorder from the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), consisting of 80 items. The original scale was field-tested using Rasch analysis for item reduction, rendering a final 43 items. NPS was further investigated among 296 seniors aged 60 years old. Rasch analysis was used to assess its construct validity. Result: Of 43 items, 17 were further removed as infit or outfit mean square >1.5. The final 26-item NPS met all necessary criteria of unidimensionality and local independence without differential item functioning due to age and sex, and good targeting with subjects. Person and item reliability were 0.88 and 0.95, respectively. No disordered threshold or category was found. Conclusions: The NPS is a promising tool with a proven construct validity based on the Rasch measurement model among Thai seniors. This new questionnaire can be used as outcome measures in clinical practice.

Clinimetric properties of the Smoking Abstinence Expectancies Questionnaire

Smoking abstinence expectancies are beliefs about negative and positive short-term psychological and physiological consequences of not smoking. The Smoking Abstinence Expectancies Questionnaire (SAEQ) is a widely used Patient-Reported Outcome Measure (PROM) to assess smoking abstinence expectancies. It has four subscales: negative mood, somatic symptoms, harmful consequences, positive consequences. Although studied from a psychometric perspective, the SAEQ needs further evaluation. Clinimetrics, and its Clinimetric Criteria for Patient-Reported Outcome Measures (CLIPROM), offers a robust method to evaluate the SAEQ. We verified construct validity and sensitivity of the Italian version of the SAEQ applying CLIPROM criteria. A total of 293 adult Italian smokers were consecutively enrolled at two smoking cessation clinics and assessed via the SAEQ. Item Response Theory models (i.e., combining Rasch and Mokken analyses) were used to test construct validity and sensitivity. The total score of the SAEQ was not found to be unidimensional but each SAEQ subscale score was. PSI (0.90) indicated that the total score of the SAEQ could reliably discriminate between respondents with different levels of the trait under assessment, whereas SAEQ subscales on negative mood and harmful consequences could reliably distinguish between different groups but not between different subjects (PSI ranging from 0.77 and 0.78). Overall, the total score of the SAEQ is a sensitive screening PROM and can be used at smoking cessation clinics to discriminate between subjects with different levels of smoking abstinence expectancies. SAEQ subscales should be used to detect severity and subjective burden of a wide range of expected effects of nicotine abstinence.

Construct validity of the Smoker Complaint Scale: A clinimetric analysis using Item Response Theory (IRT) models

A number of rating scales evaluating symptoms of nicotine withdrawal have been developed over the years but insufficient attention has been devoted to the assessment of their clinimetric properties. Clinimetrics, the science of clinical measurements, is an innovative approach, particularly useful for assessing the validity of rating scales. This is the first study using clinimetric principles to test the construct validity of the Smoker Complaint Scale (SCS), a self-rating scale specifically developed to assess acute symptoms of nicotine withdrawal. Construct validity was evaluated via Item Response Theory (IRT) models (i.e., combining Rasch and Mokken analyses). A total of 366 subjects (mean age = 34.0, SD = 11.3 years) participated in the study. IRT analyses showed that SCS was a multidimensional measure of symptoms of nicotine withdrawal, including unidimensional subscales, particularly a four-item subscale (the SCS₄), which was found to entail the clinimetric property of construct validity. IRT analyses also revealed that affective symptoms of nicotine withdrawal preceded cognitive ones. The SCS should be considered as an item bank, including a particularly valid subscale, the SCS₄ that can be used as a screening or outcome measure to evaluate the severity of cognitive and affective symptoms of nicotine withdrawal. SCS₄ is a sensitive clinimetric index which differentiates "ceiling symptoms" of nicotine withdrawal (e.g., "feeling slowed down") from "floor symptoms" of nicotine withdrawal (e.g., "feeling lightheaded") that emerge in the severe form of nicotine withdrawal.

Construct Validity and Differential Item Functioning of the PHQ-9 Among Health Care Workers: Rasch Analysis Approach

PURPOSE

The Patient Health Questionnaire (PHQ-9) is a widely used self-report questionnaire to screen depression. Its psychometric property has been tested in many populations including health care workers. We used Rasch measurement theory to examine the psychometric properties of PHQ-9 regarding item difficulty, item fit and the differences between subgroups of respondents classified by sex, age, education and alcohol user status, based on the same overall location of participants.

PATIENTS AND METHODS

In total, 3204 health care workers of Maharaj Nakorn Chiang Mai Hospital participated and were administered the PHQ-9. Rating scale Rasch measurement modeling was used to examine the psychometric properties of the PHQ-9.

RESULTS

The data fitted well to the Rasch model and no violations of the assumption of unidimensionality were observed. All 9 items could form a unidimensional construct of overall depressive severity. Suicidal ideation was the least endorsed while sleep problem was the most. No disordered category and threshold of the rating response were observed. No locally dependent items were observed. No items were found to show differential item functioning across age, sex, education and alcohol consumption. The item-person Wright map showed that the PHQ-9 did not target well with the sample, and a wide gap suggesting few or no items exist to differentiate participants at a certain ability level among the PHQ-9 items.

CONCLUSION

The PHQ-9 can be used as a screening questionnaire for major depressive disorder as its psychometric property was verified based on Rasch measurement model. The findings are generally consistent with related studies in other populations. However, the PHQ-9 may be unsuitable for assessing depressive symptoms among health care workers who have low levels of depression.

Validation of Neuro-QoL and PROMIS Mental Health Patient Reported Outcome Measures in Persons with Huntington Disease

BACKGROUND

Patient-reported outcomes (PROs) for mental health are important for persons with Huntington disease (HD) who commonly experience symptoms of depression, anxiety, irritability, anger, aggression, and apathy. Given this, there is a need for reliable and valid patient-reported outcomes measures of mental health for use as patient-centered outcomes in clinical trials.

OBJECTIVE

Thus, the purpose of this study was to establish the psychometric properties (i.e., reliability and validity) of six Neuro-QoL and PROMIS mental health measures to support their clinical utility in persons with HD.

METHODS

294 individuals with premanifest (n = 102) or manifest HD (n = 131 early HD; n = 61 late HD) completed Neuro-QoL/PROMIS measures of Emotional and Behavioral Dyscontrol, Positive Affect and Well-Being, Stigma, Anger, Anxiety, and Depression, legacy measures of self-reported mental health, and clinician-rated assessments of functioning.

RESULTS

Convergent validity and discriminant validity for the Neuro-QoL and PROMIS measures of Emotional and Behavioral Dyscontrol, Positive Affect and Well-Being, Stigma, Anger, Anxiety, and Depression, were supported in persons with HD. Neuro-QoL measures of Anxiety and Depression also demonstrated moderate sensitivity and specificity (i.e., they were able to distinguish between individuals with and without clinically significant anxiety and depression).

CONCLUSIONS

Findings provide psychometric support for the clinical utility of the Neuro-QoL/PROMIS measures of mental health measures in persons with HD. As such, these measures should be considered for the standardized assessment of health-related quality of life in persons with HD.

High Rates of Mental Health Disorders in Civilian Employees Working in Police Organizations

Working in a police organization often involves being exposed to potentially traumatic events and stressful circumstances regardless of occupation or rank. Police mental health is a public health concern, but the mental health of civilian employees working in police organizations has been much less studied. The current study aims to compare the frequency of mental health conditions in both police officers and civilians. This was evaluated by measuring mean scores on several mental health screening tools including scales to determine symptom severity for posttraumatic stress disorder (PTSD) with the PTSD Checklist - PCL-5, depression with the Patient Health Questionnaire-9 (PHQ), general anxiety with the Generalized Anxiety Disorder 7-item scale (GAD-7), and alcohol use with the Alcohol Use Disorders Identification Test (AUDIT). The total potential population was 1,225 civilian employees and 3,714 police officers, of which 513 (10%) participated. Of these, 201 (16%) were civilians, and 312 (8%) were police officers (p<0.001). In the study population, 26% screened positive for any mental health disorder. Somewhat surprisingly, we found significantly more civilians (32.8%) than police officers (22.7%) met diagnostic criteria. We also found that civilian participants had higher mean scores in measures of PTSD, anxiety, and depression, although only for depression did this reach statistical significance. Civilians were 1.7 times more likely to screen positive for depression compared to police officers, a statistically significant difference. In contrast, police officers demonstrated statistically higher scores for alcohol use than civilians. One limitation of this study is that the data reflects responses from only a minority of the overall population and, therefore, may not accurately reflect the frequency of mental health issues in the total police organization including civilian employees. Nonetheless, the results strongly suggest that the mental health of all employees can be negatively impacted by working in a police environment, and this is important given the growing number of civilians employed within police organizations. These findings support initiatives aimed at destigmatizing mental health disorders, improving stress management, and increasing access to mental health care on an organization-wide basis, and not just limited to front-line police officers.

The Accuracy of the Patient Health Questionnaire-9 Algorithm for Screening to Detect Major Depression: An Individual Participant Data Meta-Analysis

BACKGROUND

Screening for major depression with the Patient Health Questionnaire-9 (PHQ-9) can be done using a cutoff or the PHQ-9 diagnostic algorithm. Many primary studies publish results for only one approach, and previous meta-analyses of the algorithm approach included only a subset of primary studies that collected data and could have published results.

OBJECTIVE

To use an individual participant data meta-analysis to evaluate the accuracy of two PHQ-9 diagnostic algorithms for detecting major depression and compare accuracy between the algorithms and the standard PHQ-9 cutoff score of ≥10.

METHODS

Medline, Medline In-Process and Other Non-Indexed Citations, PsycINFO, Web of Science (January 1, 2000, to February 7, 2015). Eligible studies that classified current major depression status using a validated diagnostic interview.

RESULTS

Data were included for 54 of 72 identified eligible studies (n participants = 16,688, n cases = 2,091). Among studies that used a semi-structured interview, pooled sensitivity and specificity (95% confidence interval) were 0.57 (0.49, 0.64) and 0.95 (0.94, 0.97) for the original algorithm and 0.61 (0.54, 0.68) and 0.95 (0.93, 0.96) for a modified algorithm. Algorithm sensitivity was 0.22-0.24 lower compared to fully structured interviews and 0.06-0.07 lower compared to the Mini International Neuropsychiatric Interview. Specificity was similar across reference standards. For PHQ-9 cutoff of ≥10 compared to semi-structured interviews, sensitivity and specificity (95% confidence interval) were 0.88 (0.82-0.92) and 0.86 (0.82-0.88).

CONCLUSIONS

The cutoff score approach appears to be a better option than a PHQ-9 algorithm for detecting major depression.

Psychometric properties of the German version of the Leicester Cough Questionnaire in sarcoidosis

Background

Cough is one of the most common symptoms in general and pulmonary medicine with profound negative impact on health-related quality of life (HRQL). The Leicester Cough Questionnaire (LCQ) is a validated HRQL questionnaire, yet a validated German version of the LCQ is not available and it has never been tested in a cohort with sarcoidosis.

Objectives

To translate the LCQ into German and determine its psychometric properties.

Methods

The LCQ was translated in a forward-backward approach. Structured interviews in sarcoidosis patients were performed. Subsequently, sarcoidosis patients were asked to answer the German LCQ and comparative questionnaires. Distribution properties, item difficulty, concurrent validity, Rasch model fit and internal consistency of the German LCQ were determined.

Results

200 patients with sarcoidosis were included. We provide evidence for reliability, unidimensionality and internal consistency. However, only a moderate correlation with general and respiratory-specific HRQL questionnaires, no Rasch model fit could be shown. Skewed responses caused by floor effects were detected.

Conclusion

We demonstrate that the German LCQ is valid and reliable and its psychometric properties fulfil the standards required for its use in clinical settings as well as in interventional trials.

Using Person Fit Statistics to Detect Outliers in Survey Research

Context: When working with health-related questionnaires, outlier detection is important. However, traditional methods of outlier detection (e.g., boxplots) can miss participants with “atypical” responses to the questions that otherwise have similar total (subscale) scores. In addition to detecting outliers, it can be of clinical importance to determine the reason for the outlier status or “atypical” response.

Objective: The aim of the current study was to illustrate how to derive person fit statistics for outlier detection through a statistical method examining person fit with a health-based questionnaire.

Design and Participants: Patients treated for Cushing's syndrome (n = 394) were recruited from the Cushing's Support and Research Foundation's (CSRF) listserv and Facebook page.

Main Outcome Measure: Patients were directed to an online survey containing the CushingQoL (English version). A two-dimensional graded response model was estimated, and person fit statistics were generated using the Zh statistic.

Results: Conventional outlier detections methods revealed no outliers reflecting extreme scores on the subscales of the CushingQoL. However, person fit statistics identified 18 patients with “atypical” response patterns, which would have been otherwise missed (Zh > |±2.00|).

Conclusion: While the conventional methods of outlier detection indicated no outliers, person fit statistics identified several patients with “atypical” response patterns who otherwise appeared average. Person fit statistics allow researchers to delve further into the underlying problems experienced by these “atypical” patients treated for Cushing's syndrome. Annotated code is provided to aid other researchers in using this method.