Development and psychometric evaluation of a questionnaire for the assessment of depression in primary care: a cross-sectional study.

OBJECTIVES: To develop a new questionnaire for the diagnostic assessment of depression adapted to the primary care setting by combining psychiatric criteria and heuristics of general practitioners (GPs). Psychometric evaluation of the new questionnaire and first validity evidence. DESIGN: The questionnaire was developed using cognitive interviews with think-aloud technique. Factorial validity was then examined in a cross-sectional study. SETTING: Primary care. Five general practices in Bavaria, Germany. PARTICIPANTS: 15 GPs, 4 psychiatrists/psychotherapists and 13 patients participated in cognitive expert interviews. A primary care sample of N=277 consecutive patients participated in the cross-sectional study. METHODS: After consultation with experts and literature research, the questionnaire contained a self-rating part for patients and an external part for GPs. Items were then iteratively optimised using cognitive interviews. Factorial validity was examined. To estimate internal consistency, Cronbach's α was calculated. Validity was assessed by correlating the new questionnaire and the Patient Health Questionnaire-9 (PHQ-9). RESULTS: The preliminary version of the two-part 'Questionnaire for the assessment of DEpression SYmptoms in Primary Care' (DESY-PC) comprised 52 items for patients (DESY-PAT-1: questions about patient's environment; DESY-PAT-2: questions about depression-specific symptoms) and 21 items for GPs (DESY-GP). The analysis of the DESY-PAT-1 revealed a one-factor solution ('environmental factors') with Cronbach's α of 0.55. The items of the DESY-PAT-2 were assigned to three factors, 'depressive cognitions', 'suicidality' and 'symptoms of fatigue', with Cronbach's α of 0.86, 0.79 and 0.85, respectively. Factorial analysis revealed two factors for the DESY-GP: 'depression symptoms' and 'medical history/external factors'. Cronbach's α was 0.90 and 0.59, respectively. After factorial analysis, the DESY-PAT was reduced to 28 items, and the DESY-GP was reduced to 15 items. Correlations of the DESY-PC with the PHQ-9 were high and significant, indicating convergent validity. CONCLUSIONS: The new questionnaire represents an innovative extension of depression questionnaires and could be particularly suitable for general practices.

Lessons learned from applying established cut-off values of questionnaires to detect somatic symptom disorders in primary care: a cross-sectional study.

Introduction: Based on two diagnostic accuracy studies in high-prevalence settings, two distinctly different combinations of cut-off values have been recommended to identify persons at risk for somatic symptom disorder (SSD) with the combination of the Patient-Health Questionnaire-15 (PHQ-15) and the Somatic Symptom Disorder-B Criteria Scale (SSD-12). We investigated whether the reported sensitivity and specificity of both recommended cut-off combinations are transferable to primary care. Methods: In a cross-sectional study, 420 unselected adult primary care patients completed PHQ-15 and SSD-12. Patients scoring ≥9 and ≥ 23 (recommended cut-off combination #1) or ≥ 8 and ≥ 13 (recommended cut-off combination #2) were considered test-positive for SSD, respectively. To assess the validity of the reported sensitivity and specificity in different low- to high-prevalence settings, we compared correspondingly expected proportions of test positives to the proportion observed in our sample. Results: Based on combination #1, 38 participants (9%) were found to be test positive, far fewer than expected, based on the reported values for sensitivity and specificity (expected minimum frequency 30% with a true prevalence ≥1%). This can only be explained by a lower sensitivity and higher specificity in primary care. For combination #2, 98 participants (23%) were test positive, a finding consistent with a true prevalence of SSD of 15% or lower. Discussion: Our analyzes strongly suggest that the sensitivity and specificity estimates reported for combination #1 are not applicable to unselected primary care patients and that the cut-off for the SSD (≥23) is too strict. Cut-off combination #2 seems more applicable but still needs to be tested in studies that compare screening findings by questionnaires with validated diagnostic interviews as reference standards in primary care populations.

Combining the GP's assessment and the PHQ-9 questionnaire leads to more reliable and clinically relevant diagnoses in primary care.

BACKGROUND: Screening questionnaires are not sufficient to improve diagnostic quality of depression in primary care. The additional consideration of the general practitioner's (GP's) assessment could improve the accuracy of depression diagnosis. The aim of this study was to examine whether the GP rating supports a reliable depression diagnosis indicated by the PHQ-9 over a period of three months. METHODS: We performed a secondary data analysis from a previous study. PHQ-9 scores of primary care patients were collected at the time of recruitment (t1) and during a follow-up 3 months later (t2). At t1 GPs independently made a subjective assessment whether they considered the patient depressive (yes/no). Two corresponding groups with concordant and discordant PHQ-9 and GP ratings at t1 were defined. Reliability of the PHQ-9 results at t1 and t2 was assessed within these groups and within the entire sample by Cohen's Kappa, Pearson's correlation coefficient and Bland-Altman plots. RESULTS: 364 consecutive patients from 12 practices in the region of Upper Bavaria/Germany participated in this longitudinal study. 279 patients (76.6%) sent back the questionnaire at t2. Concordance of GP rating and PHQ-9 at t1 led to higher replicability of PHQ-9 results between t1 and t2. The reliability of PHQ-9 was higher in the concordant subgroup (κ = 0.507) compared to the discordant subgroup (κ = 0.211) (p = 0.064). The Bland-Altman Plot showed that the deviation of PHQ-9 scores at t1 and t2 decreased by about 15% in the concordant subgroup. Pearson's correlation coefficient between PHQ-9 scores at t1 and t2 increased significantly if the GP rating was concordant with the PHQ-9 at t1 (r = 0.671) compared to the discordant subgroup (r = 0.462) (p = 0.044). CONCLUSIONS: The combination of PHQ-9 and GP rating might improve diagnostic decision making regarding depression in general practices. PHQ-9 positive results might be more reliable and accurate, when a concordant GP rating is considered.