Author's response to reviews Title: Reliability and validity of the Thai version of the PHQ-9 Authors (original) (raw)
Thank you very much for giving us the opportunity to revise our manuscript. We would like to thank the reviewers' for giving us the highly valuable comments to improve our manuscript. We have revised the manuscript in accordance with all the reviewers' comments. A point-by-point response to the comments is given below. We hope that the revised manuscript and our responses are satisfactory to you. Thank you for your consideration. We look forward to hearing your reply. Sincerely yours, Manote Lotrakul, M.D. Reviewer 1: Yvonne Forsell General 1. The paper presents a carefully designed study concerning the validity and reliability of the Thai version of the PHQ-9. It is clearly written and easy to understand. However it needs some editing of the English since there are several grammatical errors as well as spelling errors.. Response: The final manuscript will be sent to a native English speaking colleague for language revision. 2. ...The number of depressed is surprisingly low (1.9%) but as the author states this could have been due to a selection bias. This would mean that people who were depressed had chosen to go to the psychiatrists instead of to the GPs. However it could also mean that the PHQ-9 does not capture depression due to underreports of symptoms. Response: We agree with the reviewer. We have included this suggestion in the discussion section on limitations of the study-"Second, there was a possibility that a proportion of participants might have underreported their depressive symptoms on both the PHQ-9 and the MINI clinical interview." (page 15, 3rd paragraph) Major Compulsory Revisions 1. The statement that PHQ-9 was the optimal measure to establish a categorical diagnosis of depression is not supported. The authors might mean when comparing to PHQ-9 used as a continuous measure. Response: We thank the reviewer for her thoughtful comment. This section has been revised to provide more clarity. Result of the PHQ-9 categorical algorithm for detecting major depression showed that it is less useful than the cutoff score for a screening purpose. 2. A ROC curve is presented and the area under the curve is 0.89. The authors state that this means that the PHQ-9 is a good test to identify patients with depressive disorder. This is not entirely true, a better way to analyse the performance of PHQ-9 would be to use QROC curves. Response: We have revised the statement about the AUC value as "The area under the curve (AUC) in this study was 0.89 (SD=0.05, 95% CI 0.85 to 0.92) which demonstrated a moderate accuracy [21]." We thank the reviewer for her kind suggestion of the QROC curves. We agree that this is a better way to analyze the performance of PHQ-9. However, this involves a somewhat sophisticated statistical analysis and a software which is difficult for us to access. As most articles so far report the performance of a screening tool using the ROC curve, we hope that the reviewer accept our request to retain the original ROC curve for analyzing the performance of the PHQ-9.
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