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Comment & Response |

Error in Calculating Main Outcome in Gamma Ventral Capsulotomy for Obsessive-Compulsive Disorder Randomized Clinical Trial FREE

Christopher Baethge, MD1
[+] Author Affiliations
1Department of Psychiatry and Psychotherapy, University of Cologne Medical School, Cologne, Germany
JAMA Psychiatry. 2015;72(12):1257-1258. doi:10.1001/jamapsychiatry.2015.0667.
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Published online

To the Editor In many ways, the Lopes and coauthors randomized clinical trial1 on gamma ventral capsulotomy (GVC) in patients with treatment-refractory obsessive-compulsive disorder stands out. Ethics approval and informed consent procedures are exemplary for a contemporary study in psychosurgery. Patients were followed up for an exceptionally long period. The article is among the few in psychiatry documenting blinding of raters and patients, although such data are not only important, as presented, at follow-up but particularly immediately after surgery (as apparently ascertained).2 Further, the authors make their study transparent in providing a wealth of outcome data.

It appears from these data that a small error occurred in calculating the main outcome: Table 1 and the P value for comparing the decrease in Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) scores between treatment and control indicate the baseline Y-BOCS score of the third patient in the treatment group (ATa3) was not 36 but 30. With a follow-up score of 22, the decrease was 26.7%, rather than 38.9%, as stated in Table 2. Apparently, however, Lopes et al concluded from the latter figure that patient 3 was a responder because the decrease exceeded 35%. Without this patient, the number of responders under GVC stands at 2 of 8, with no responder among controls (Fisher exact test: P = .47). The absolute risk reduction, therefore, is reduced from statistically significant 37.5% (95% CI, 4% to 71%) to 25% (95% CI, −5% to 55%; nonsignificant), and number needed to treat increases to 4 (95% CI, 1.7 to ∞). Given group sizes of 8, Y-BOCS score change, when compared as a continuous variable, should be analyzed using the exact Mann-Whitney U test and not its asymptotic version.3 Thus, P slightly rises from .046 to .050 (or to .0499, to be exact). Similarly, when recalculated, the P value for change in Dimensional Y-BOCS score increased from 0.01 to 0.02. These differences are not entirely moot in a study with a host of outcomes and not adjusted for multiple tests. As a consequence, corrected figures for both dichotomous and continuous outcomes (calculated with Open Epi4 and SPSS version 22 [IBM]) suggest that chance cannot be ruled out as a factor in explaining the results.

The corrections do not lessen the merit of this exceptional study, yet the bottom line of the randomized clinical trial may be this: We cannot be sure, but it seems as if GVC reduced symptoms in treatment-resistant obsessive-compulsive disorder. Two of 8 patients responded to treatment, and another patient developed delirium, likely as a consequence of GVC. Depression, anxiety, and quality of life were not improved.

ARTICLE INFORMATION

Corresponding Author: Christopher Baethge, MD, Department of Psychiatry and Psychotherapy, University of Cologne Medical School, Cologne, Germany (cbaethge@uni-koeln.de).

Published Online: October 28, 2015. doi:10.1001/jamapsychiatry.2015.0667.

Conflict of Interest Disclosures: None reported.

REFERENCES

Lopes  AC, Greenberg  BD, Canteras  MM,  et al.  Gamma ventral capsulotomy for obsessive-compulsive disorder: a randomized clinical trial. JAMA Psychiatry. 2014;71(9):1066-1076.
PubMed   |  Link to Article
Baethge  C, Assall  OP, Baldessarini  RJ.  Systematic review of blinding assessment in randomized controlled trials in schizophrenia and affective disorders 2000-2010. Psychother Psychosom. 2013;82(3):152-160.
PubMed   |  Link to Article
Mann  HB, Whitney  DR.  On a test of whether one or two random variables is stochastically larger than the other. Ann Math Stat. 1947;18(1):50-60. doi:10.1214/aoms/1177730491.
Link to Article
Dean  AG, Sullivan  KM, Soe  MM. Open Epi: open source epidemiologic statistics for public health. http://www.OpenEpi.com. Accessed March 28, 2015.

Figures

Tables

References

Lopes  AC, Greenberg  BD, Canteras  MM,  et al.  Gamma ventral capsulotomy for obsessive-compulsive disorder: a randomized clinical trial. JAMA Psychiatry. 2014;71(9):1066-1076.
PubMed   |  Link to Article
Baethge  C, Assall  OP, Baldessarini  RJ.  Systematic review of blinding assessment in randomized controlled trials in schizophrenia and affective disorders 2000-2010. Psychother Psychosom. 2013;82(3):152-160.
PubMed   |  Link to Article
Mann  HB, Whitney  DR.  On a test of whether one or two random variables is stochastically larger than the other. Ann Math Stat. 1947;18(1):50-60. doi:10.1214/aoms/1177730491.
Link to Article
Dean  AG, Sullivan  KM, Soe  MM. Open Epi: open source epidemiologic statistics for public health. http://www.OpenEpi.com. Accessed March 28, 2015.

Correspondence

December 1, 2015
Stephan Heckers, MD; Howard Bauchner, MD; Annette Flanagin, RN, MA
1JAMA Psychiatry, Nashville, Tennessee
2JAMA and The JAMA Network, Chicago, Illinois
JAMA Psychiatry. 2015;72(12):1170-1171. doi:10.1001/jamapsychiatry.2015.2278.
September 1, 2014
Antonio C. Lopes, MD, PhD; Benjamin D. Greenberg, MD, PhD; Miguel M. Canteras, MD; Marcelo C. Batistuzzo, PsyD; Marcelo Q. Hoexter, MD, PhD; André F. Gentil, MD; Carlos A. B. Pereira, PhD; Marinês A. Joaquim, RN; Maria E. de Mathis, PsyD; Carina C. D’Alcante, PsyD, MSc; Anita Taub, PsyD, MSc; Douglas G. de Castro, MD; Lucas Tokeshi, MD; Leonardo A. N. P. C. Sampaio, MD; Cláudia C. Leite, MD, PhD; Roseli G. Shavitt, MD, PhD; Juliana B. Diniz, MD, PhD; Geraldo Busatto, MD, PhD; Georg Norén, MD, PhD; Steven A. Rasmussen, MD, PhD; Eurípedes C. Miguel, MD, PhD
1Department and Institute of Psychiatry, University of São Paulo School of Medicine, São Paulo, Brazil
2Department of Psychiatry and Human Behavior, The Warren Alpert Medical School of Brown University, Providence, Rhode Island
3The Institute of Neurological Radiosurgery, Hospital Santa Paula, São Paulo, Brazil
4Statistics Department of the Mathematics and Statistics Institute of the University of São Paulo, São Paulo, Brazil
5Department of Radiology, University of São Paulo School of Medicine, São Paulo, Brazil
6Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Providence, Rhode Island
2Department of Psychiatry and Human Behavior, The Warren Alpert Medical School of Brown University, Providence, Rhode Island6Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Providence, Rhode Island
JAMA Psychiatry. 2014;71(9):1066-1076. doi:10.1001/jamapsychiatry.2014.1193.
December 1, 2015
Antonio C. Lopes, MD, PhD; Benjamin D. Greenberg, MD, PhD; Carlos A. B. Pereira, PhD; Georg Norén, MD, PhD; Euripedes C. Miguel, MD, PhD
1Department and Institute of Psychiatry, University of São Paulo (USP) School of Medicine, São Paulo, Brazil
2Department of Psychiatry and Human Behavior, The Warren Alpert Medical School of Brown University, Providence, Rhode Island3Department of Neurosurgery, The Warren Alpert Medical School of Brown University, Providence, Rhode Island
4Statistics Department of the Mathematics and Statistics Institute of the University of São Paulo, São Paulo, Brazil
JAMA Psychiatry. 2015;72(12):1258. doi:10.1001/jamapsychiatry.2015.0673.
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