BOCA RATON, FLA. – "Just what we need – another scale," Dr. Mark Zimmerman said, tongue-in-cheek, as he started to explain why he and his colleagues developed the Remission From Depression Questionnaire.
Current measures define remission based on a lack of depressive symptoms alone, which is insufficient, Dr. Zimmerman said at the annual meeting of the New Clinical Drug Evaluation Unit, sponsored by the National Institute of Mental Health.
Dr. Mark Zimmerman
In a previous study of 514 depressed outpatients (J. Psychiatr. Res. 2008;42:797-801), "we found symptom resolution was not the most important consideration of depression remission," Dr. Zimmerman said. "Multiple factors were identified, so from a patient point of view, symptom-based definitions of remission are too narrow."
So Dr. Zimmerman and his colleagues developed the multidimensional Remission From Depression Questionnaire (RDQ), and conducted two studies to test reliability, validity, and patient preferences.
The RDQ assesses seven constructs: symptoms of depression, other symptoms, coping ability, positive mental health, functioning, life satisfaction, and general sense of well being. When the researchers compared remitters to nonremitters, significant differences were found on the RDQ total scale, depressive symptoms, and other symptoms. These findings support the RDQ as a valid measure, said Dr. Zimmerman, director of outpatient psychiatry at Rhode Island Hospital and with the department of psychiatry and human behavior at Brown University, both in Providence.
In the first study, Dr. Zimmerman and his colleagues compared responses from 102 depressed outpatients on the 41-item RDQ and the 16-item Quick Inventory of Depressive Symptomatology (QIDS). "They did not know we had developed one of these measures," he said.
There were no differences between the two measures on completion time. They were "equally burdensome and equally understandable," Dr. Zimmerman said.
Participants also reported their preference using a nine-item measure. Twice as many reported the RDQ more accurately described their overall state, 48%, vs. 24% for the QIDS. Nearly half said they preferred to complete the RDQ, 46%, compared with 22% who preferred completing the QIDS.
"Our conclusion from the first study is ... patients prefer the multifactorial RDQ scale more than a symptoms-based measure."
In a second study, the investigators asked 247 mildly depressed outpatients in ongoing treatment to complete the RDQ. The QIDS average score was 9.8, and the Hamilton Depression Rating Scale average score was 8.6. The RDQ correlated 0.62 with Hamilton scale and 0.70 with the Clinical Global Impression-Severity scale.
Dr. Zimmerman and his colleagues also split the cohort into remitters vs. nonremitters. Significant differences were found between these groups on the RDQ total score, 18 vs. 43; the depressive symptoms score, 5 vs. 12; and the other symptoms score, 2.8 vs. 5.7.
"The RDQ is a reliable and valid measure that evaluates multiple domains," Dr. Zimmerman said.
A group of 60 of the 247 patients waited and completed the RDQ measure a second time to test its reliability. The test-retest reliability and internal consistency were all greater than 0.8, Dr. Zimmerman said.
The next step is to assess the RDQ as an outcome measure in an acute treatment study of depression, Dr. Zimmerman said. An unanswered question is: Does the RDQ do a better job of predicting relapse compared to just a symptom-based scale?
Dr. Zimmerman said he had no disclosures. The studies were funded by Eli Lilly.