Rapid detection of major depression in epilepsy: a multicentre st
Gilliam FG, Barry JJ, Hermann BP, Meador KJ, Vahle V, Kanner AM;
Commented by , 23 Jun 2006
Background
Major depression is highly prevalent in epilepsy, yet it is not routinely assessed in neurology clinics (ref. 1).
Aim
To develop a simple screening tool for epilepsy-associated depression.
Methods
- A questionnaire of 46 items was developed to identify symptoms of depression that do not overlap with common comorbid cognitive deficits and side effects of antiepileptic drugs (AEDs)
- The questionnaire, together with other validated instruments for diagnosing depression, health status and adverse effects of AEDs was tested in 205 adults with epilepsy at 5 U.S. centres
- discriminant function analysis was used to identify the most efficient items. The resulting instrument (Neurological Depression Inventory for Epilepsy, NDDI-E) was verified in a separate set of 229 patients.
Results
- The NDDI-E included 6 items only, had an internal consistent reliability of 0.85 and a test-re-test reliability of 0.78
- A NDDI-E score >15 had a specificity of 90%, a sensitivity of 81% and a positive predictive value of 0.61 for a diagnosis of major depression
- An optimum cutoff at >15 was confirmed in the verification study
- Unlike the Beck’s Depression Inventory (BDI) and the Center for Epidemiological studies depression scale (CES-D), the NDDI-score the NDDI-score’s association with major depression was not affected by the adverse e4ffect profile (ref. 2) of AEDs.
Professor Perucca's comments
Major depression is a common comorbidity in epilepsy. It has been reported in >30% of patients in a comunity-based study (ref. 3)and in 20-55% of patients in tertiary referral clinics (ref. 4; ref. 5; ref. 6). Together with adverse effects of AEDs, depression is strongly associated with poor quality of life in these patients (ref. 7; ref. 8). Yet, it is not routinely investigated in most neurology clinics (ref. 1).
This work of Frank Gilliam and his colleagues is important because it led to the development of a promising new instrument to screen for major depression in the routine clinical setting. The instrument has a number of attractive features:
- It is is simple, being based on a brief set of symptoms
- Its positive predictive value, sensitivity and specificity compare favorably with other available instruments for people with epilepsy, such as the BDI and the CES-D
- Unlike the BDI and the CES-D, it does not include common adverse effects of AEDs which mimic symptoms of depression.
Although the adverse event profile was correlated with the NDDI-E score, both instruments independently correlated with overall health statuts as estimated by the QOLI-89 questionnaire. In fact, the combination of the NDDI-E and the adverse events profile explained more than 70% of the variance in QOLIE-89 total score.
An interesting feature of that optimization of the NDDI-E items led to exclusion of "sadness" and "irritability". This is in agreement with evidence that depression in focal epilepsy is more associated with frustration, anhedonia and hopelessness than with sadness of depressed mood (ref. 9).
The authors speculate that this could be related to temporal lobe dysfunction in the presence of intact frontal lobe function – if that was the case, the features of epilepsy-associated depression (and the validity of the NDDI-E score) would be expected to differ depending on location of the epileptic focus.
The authors acknowledge that their work has limitations. The instrument was assessed in tertiary care epilepsy clinics in the U.S., and might not be equally applicable into community-based patients or other setting. The features of epilepsy-associated depression may be more complex and atypical than major depression in other populations. Finally, the instrument is intended only for screening, and is no substitute for clinical judgement or specialised psychiatric assessment.
References
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