Association of higher costs with symptoms and diagnosis of depression

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Original Research

Association of higher costs with symptoms and diagnosis of depression

J Fam Pract. 2002 June;51(6):540-544

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References

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At study entrance or exit, 130 patients were identified with significant symptoms of depression (BDI > 8) by meeting criteria for moderate or severe depression¹⁹ and thus identifying roughly the top quartile of BDI scores among participants. This proportion approximates that of primary care patients estimated to experience significant depression.^6,7

Medical Outcomes Studies Short Form-36. Health status was measured with the MOS SF-36,²⁰ a 36-item self-report questionnaire. Reliability has been verified for difficult populations.²³ Summary measures can describe a physical component score and a mental component score.^24,25 The physical component score was used in this study to measure physical health status.

Medical chart review. Two physicians (K.D.B. and J.A.R.) reviewed the charts to identify notations of depression on problem lists and in visit notes to signify physician diagnosis of depression.

Charges. Charges were used as a proxy for costs. Electronic data for all health system charges were monitored from the initial visit through 1 full year of care. Six categories were monitored: primary care, specialty care, laboratory testing, emergency department, hospitalization, and total charges. Pharmacy charges were excluded because some patients purchased prescriptions outside the hospital system.

Statistical procedures

Mean log values for each area of medical charges were determined and contrasted with the Duncan multiple range test²⁶ to explore the first hypothesis that charges are associated with symptoms and diagnoses of depression. Next, a double hurdle model was used to test the hypotheses that depressive symptoms and physician diagnosis of depression predict the occurrence and magnitude of charges for a variety of services.^27,28 In a double hurdle model, the first “hurdle,” or step, involves exploring whether there are variables that can significantly predict the occurrence of an event (such as a medical charge). The second step involves exploring whether there are variables that can predict the magnitude of the event (eg, a medical charge).

Log-transformation of charges was performed to eliminate undue influence from outliers. No logistic regression models were developed for the occurrence of primary care charges or total charges (the first hurdle) because all study patients had charges in both categories. Results are presented by hypothesis.

Results

Seventy-seven of 508 study patients (15.1%) were identified as depressed by their primary care providers in chart notes. BDI scores showed considerable spread (range, 0–31) and were significantly associated with the diagnosis of depression (P < .001). Whereas 140 patients reported BDI scores of at least 9, only 36 of these patients were diagnosed as depressed by their physicians. Similarly, 41 patients were diagnosed as depressed despite reporting low (normal) BDI scores. Patients were assigned to 1 of 4 groups: those diagnosed as depressed and having high (abnormal) BDI scores (n = 36); those diagnosed as depressed despite low BDI scores (n = 41); those not diagnosed as depressed despite high BDI scores (n = 94); and those not diagnosed as depressed and not having high BDI scores (n = 337).

Hypothesis 1: overall impact of symptoms and diagnosis on charges

Groups diagnosed with depression had significantly higher log primary care charges than did those not diagnosed (Table 1). Both groups diagnosed with depression showed the highest primary care and total medical charges. Patients diagnosed with depression and reporting high BDI scores had higher specialty charges than those not depressed. Highest laboratory costs were found for those diagnosed as depressed despite low BDI scores and those with elevated BDI scores who were not diagnosed as depressed. There were no significant differences among groups for log charges for emergency care and hospital charges.

TABLE 1
Log charges of care by diagnosis and symptoms of depression

	Diagnosis of depression		No diagnosis of depression
Charges^†	BDI ≥ 9	BDI < 9	BDI ≥ 9	BDI < 9
Primary care	5.868*	6.054*	5.431	5.347
Specialty care	4.266*	3.742*	3.332	2.927
Emergency care	1.681	2.172	1.604	1.248
Laboratory tests	6.121	6.473^‡	6.357^‡	5.401
Hospital charges	2.174	3.742	1.548	1.1893
Total charges	7.704	7.878	7.508	6.979
*Log costs were higher for patients with the diagnosis of depression regardless of BDI score than for those with no diagnosis and a BDI below 9.
^† All charges are logarithmic.
^‡ Log costs were higher for patients with the diagnosis of depression and a BDI score below 9 or no diagnosis and a BDI score of at least 9 than for those with no diagnosis and a BDI score below 9.
BDI, Beck Depression Inventory.

Hypotheses 2 and 3: factors predicting occurrence and magnitude of charges

Cost models are presented as regressions in Table 2. The left side of the table presents logistic regressions exploring which variables predict whether or not a patient accrues charges in all areas except primary care and total charges. Because all patients had at least 1 primary care visit charge and, hence, a total charge, it was not possible to develop a model to predict the occurrence of those charges.