Commentary

Depressive illness is common and disabling and is mostly managed in primary care without recourse to specialist services. Received wisdom is that management is suboptimal: up to 50% of depressive conditions are missed by practitioners, and treatment of diagnosed patients is of inadequate intensity and duration. Educational interventions for practitioners that use clinical guidelines to improve recognition and management have been evaluated, but they have shown no benefit.

At least 3 hypotheses may explain this failure: education may be insufficient to change practitioner behaviour, study design may have been inadequate to detect true benefit, or the principles on which guidelines are based may be at fault. The last reason is likely because most of the evidence base comes from secondary care, reflecting a lack of research in primary care. “Sensitivity” of practitioners has been emphasised at the expense of “specificity,” which may result in a failure to target patients who would benefit most from more intensive management.

The studies by Katzelnick et al and Simon et al report the efficacy and cost effectiveness of a practice based intervention to improve depression management in the managed care context of 3 US HMOs. In a 2 stage screening procedure, patients with consultation rates above the 85th centile for ≥2 years were identified, and those in whom evidence existed of untreated depressive disorder (Diagnostic and Statistical Manual, Fourth Edition, diagnosis and HDRS score ≥15) were recruited (about 5% of the total registered population). Half the sample had ≥1 comorbid chronic physical illness, presumably accounting in part for their high consultation rates. The study had high completion rates, but only patients enrolled with the HMO for ≥2 years were eligible. This study characteristic limits the generalisability of the work to other settings (such as general practice) and biases the results against such groups as the long term unemployed or the elderly.

DMPs have already been shown to be of benefit to unselected depressed patients in primary care. In this study, patients in the DMP had better outcomes than those receiving usual care, with significantly greater reductions in depression scores and higher quality of life ratings. The authors estimate a number needed to treat of 5 to achieve 1 additional remission, although it is not clear how remission was defined for this calculation. The 2 studies were screening studies, however, and the “number needed to screen” to achieve 1 additional remission is close to 17. Consultation rates in the intervention group increased, whereas those in the usual care group decreased slightly.

It is not possible to identify which component of the programme was most beneficial, but it seems probable on clinical grounds that the initial visit for assessment and initiation of management (which did not occur in the usual care group) would have had considerable effect.

In analysing the cost effectiveness of the programme, the construct of “depression free days” was used. It is important to understand how these days were derived. As depression scores were only assessed at 6 weeks and 3, 6, and 12 months, most of the data were interpolated. HDRS scores ≤7 were taken as “depression free” (score 0), whereas scores ≥22 were taken as “fully symptomatic” (score 1). Linear interpolation was used to model recovery, allowing calculation of a number between 0 and 1 for each day; “depression free days” were then calculated by dividing the total scores by the number of days in the period between estimates. This construct is clearly notional, and its name is misleading because many of the periods contained no true depression free days, only partial depression free days.

The costs of the intervention appear high, and no evidence existed of the hoped for “cost offset” effect by reduction in other sources of healthcare costs, perhaps not surprising given the high prevalence of comorbid physical illness. The authors observe that the study was insufficiently powered to compare frequency of inpatient admission, which is costly; this lack might have led to failure to detect benefits. The study also had only a 1 year follow up, and benefits may take longer to be detected.

The clinical bottom line is that it is possible to identify unmet needs and improve outcomes in this segment of the primary care population, but substantial additional resources are required. Although these are not out of line with the costs of treating other important conditions, priorities have to be established to permit shifting of existing resources away from other therapeutic areas or investment of greater resources in this one.