Brief Screening Questions For Depression in Chiropractic Patients With Low Back Pain: Identification of Potentially Useful Questions and Test of Their Predictive Capacity
Alice Kongsted, Benedicte Aambakk, Sanne Bossen and Lise Hestbaek
The Nordic Institute of Chiropractic and Clinical Biomechanics,
5230 Odense, M, Denmark
Background Depression is an important prognostic factor in low back pain (LBP) that appears to be infrequent in chiropractic populations. Identification of depression in few patients would consequently implicate screening of many. It is therefore desirable to have brief screening tools for depression. The objective of this study was to investigate if one or two items from the Major Depression Inventory (MDI) could be a reasonable substitute for the complete scale.
Methods The MDI was completed by 925 patients consulting a chiropractor due to a new episode of LBP. Outcome measures were LBP intensity and activity limitation at 3-months and 12-months follow-up. Single items on the MDI that correlated strongest and explained most variance in the total score were tested for associations with outcome. Finally, the predictive capacity was compared between the total scale and the items that showed the strongest associations with outcome measures.
Results In this cohort 9% had signs of depression. The total MDI was significantly associated with outcome but explained very little of the variance in outcome. Four single items performed comparable to the total scale as prognostic factors. Items 1 and 3 explained the most variance in all outcome measures, and their predictive accuracies in terms of area under the curve were at least as high as for the categorised complete scale.
Conclusions Baseline depression measured by the MDI was associated with a worse outcome in chiropractic patients with LBP. A single item (no. 1 or 3) was a reasonable substitute for the entire scale when screening for depression as a prognostic factor.
From the FULL TEXT Article:
Pain and depression often co-exist [1-3] , and although the causal relation between the two is not clear, [4, 5] evidence suggests that pain negatively affects outcome in depression as well as vice versa .
Low back pain (LBP) is a highly frequent pain condition with a substantial impact on global health  for which the risk of a poor prognosis is increased in the presence of depression [8, 9] . It is a condition for which there is no generally effective treatment, but non-pharmacological treatment addressing psychological symptoms in addition to the physical symptoms has been demonstrated to improve outcome in LBP patients with high scores on psychological questions .
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Chiropractors see a large number of LBP patients who appear to be a population with relatively low frequency of severe psychological distress [11-13] . Nevertheless, a substantial proportion with borderline depressive scores has been observed  . Therefore, to improve care and to predict prognosis, it may be important to identify psychological factors, including depression, among those seeking care for LBP, also in chiropractic practice. For that purpose screening instruments generally perform better than clinical impressions [14, 15] , and a number of questionnaires screening for depression exist  . The Major Depression Inventory is thoroughly validated as a diagnostic screening instrument [17, 18] and has been shown to be feasible in chiropractic care . However, it is unknown if the MDI predicts outcome in chiropractic patients.
Despite the potential implications for management and prognosis, routine screening for psychological factors is not widely implemented  and has met some resistance from clinicians . One reason might be that the questionnaires are too extensive for routine clinical use where information on a variety of other prognostic factors is also relevant to collect. This is especially true in chiropractic practice where the subpopulation with depressive symptoms is small, [11-13] and therefore the identification of these relatively rare cases involves screening of many for whom it has no relevance.
If systematic screening for depression is to be implemented, there is a need for a very short and easily completed tool. Fair to good diagnostic accuracies of one-and two-item screening tools with full questionnaires for depression as reference standards have been demonstrated [21-23]. It is unknown whether observed variations are due to differences between screening questions or between screened populations, and it is possible that suitable screening questions differ between populations. Furthermore, the usefulness of brief screening questions for prediction of prognosis is unrevealed.
The aim of this study was to investigate whether the MDI is predictive of outcome in chiropractic practice and if so, whether one or two items from the MDI could potentially be used as an ultra-short tool for capturing depressive symptoms in LBP patients seeking chiropractic care. To obtain that we tested whether the total MDI was associated with 3- and 12-months outcomes, explored which single items of the MDI correlated best with the total score, and compared the predictive capacity of these items to that of the total MDI.