Abstract
Background/Aims The study aims to discover the prevalence of PHQ-9 use in primary care provider (PCP) clinical practice over a 7-year timeframe, and to determine the effect of PHQ-9 data on PCP diagnosing clinical depression and prescribing antidepressant drugs in clinical practice.
Methods We conducted a retrospective case series study analyzing data in the electronic medical records of Essentia Health, a large healthcare delivery system in Upper Midwest from 01/01/2005–12/31/2011. All patients age ≥18 managed by a PCP were included. Data collected: patient demographics, provider descriptors, PHQ-9 data, ICD-9CM depression codes, and antidepressant drugs. Analytical tests included Cochran-Armitage test for trend, Cochran-Mantel-Haenszel test and logistic regression modeling for year of maximum PHQ-9 score. PHQ-9 tests were considered independent only if they were: initial events; 10+ months after the most recent test; or immediately following a prior test with a total score of less than 5(normal). The logistic regression model included any depression diagnosis (DEP), year, sex, age, maximum PHQ-9 score-5 categories from Normal to Severe Depression, any PCP measured PHQ-9, and any behavioral health measured PHQ-9.
Results Study population included 294 PCP (~181 annually) and 216,494 patients (~105,240 annually). The measurement of independent PHQ-9 in patients managed by primary care providers increased from 0.7% (2005) to 13.5% (2011); Z = 153.34, P <0.001. Patients with an independent PHQ-9 test were 17.87 (95% CI: 17.43–18.31) times more likely to have a diagnosis of depression. After adjustment in the logistic model, patients with DEP were more likely to be prescribed an antidepressant drug, rate ratio = 3.56 (3.33–3.80). As PHQ-9 scores increased, associated rate ratios (compared to normal PHQ-9) increased incrementally, 1.26 (1.82-1.35), 2.07 (1.90–2.25), 3.05 (2.79–3.34), and 4.18 (3.72–4.70), for PHQ-9 scores 5–9, 10–14, 15–19 and 20+, respectively.
Conclusions Our study found PHQ-9 use in primary care clinical practice increased significantly over 7 years. Patients having PHQ-9 testing in primary care were more likely to have a diagnosis of depression. Patients with increased severity of PHQ-9 scores were substantially more likely to be prescribed an antidepressant drug. PHQ-9 data appear to increase the diagnosis of clinical depression and prescribing of antidepressant drugs in primary care.
