Development of a prognostic model for predicting depression severity in adult primary patients with depressive symptoms using the diamond longitudinal study

Depression trajectories among primary care patients are highly variable, making it difficult to identify patients that require intensive treatments or those that are likely to spontaneously remit. Currently, there are no easily implementable tools clinicians can use to stratify patients with depressive symptoms into different treatments according to their likely depression trajectory. We aimed to develop a prognostic tool to predict future depression severity among primary care patients with current depressive symptoms at three months. Patient-reported data from the diamond study, a prospective cohort of 593 primary care patients with depressive symptoms attending 30 Australian general practices. Participants responded affirmatively to at least one of the first two PHQ-9 items. Twenty predictors were pre-selected by expert consensus based on reliability, ease of administration, likely patient acceptability, and international applicability. Multivariable mixed effects linear regression was used to build the model. The prognostic model included eight baseline predictors: sex, depressive symptoms, anxiety, history of depression, self-rated health, chronic physical illness, living alone, and perceived ability to manage on available income. Discrimination (c-statistic =0.74; 95% CI: 0.70–0.78) and calibration (agreement between predicted and observed symptom scores) were acceptable and comparable to other prognostic models in primary care. More complex model was not feasible because of modest sample size. Validation studies needed to confirm model performance in new primary care attendees. A brief, easily administered algorithm predicting the severity of depressive symptoms has potential to assist clinicians to tailor treatment for adult primary care patients with current depressive symptoms. •Model developed to predict future depression severity in primary care patients.•Prognostic model is brief and easily administered in a busy primary care setting.•Model using psychosocial items is embedded in a clinical prediction tool (CPT).•CPT tailors type and intensity of treatment to predicted depression severity.•Is a systematic approach designed to support clinician treatment decision making.