Electronic letters to:
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eLetters: Electronic letters published:
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Response to question regarding duplication of publication
- Sandra Dial (18 December 2006)
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Duplication of results?
- Adam D Porath (18 December 2006)
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Sandra Dial McGill University
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sandra.dial{at}mcgill.ca Sandra Dial
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The oral vancomycin study grew out of criticism of the group defined by a “clincal diagnosis” in the JAMA paper, as well as the issues raised by Van Staa et al re changes in recording. We wished to look at treatment around the diagnosis to “tighten” the case definition. We then found the following, approximately 90% of patients (approx 6000) who had a Cdiff toxin assay performed had no result entered in the laboratory results section. We also found that there were 2 different coding systems for medical diagnoses – OXMIS and READ – in practices using OXMIS coding there was no defined medical diagnostic code for CDAD – so these practices may have been missed in our original study. We believe that the lab results and clinical diagnosis may have been included in the free text which we did not have access to. Also in the JAMA study, if the test was done and no results were entered these patients were excluded if they did not have a clinical diagnosis, we possibly missed cases as a result of this. We believe the oral vanco patients allowed us to find cases from OXMIS practices and possibly patients whose toxin assay results or clinical diagnosis might have been entered in the free text only . In the JAMA study many cases were included based on toxin assay as since 2002 direct electronic transfer of lab results into the research database began. As written in the manuscript defining cases based on a prescription was less likely to be affected by time related changes in data entry and recording. We mentioned that they cases did not overlap many times in the manuscript that the cases reported in this study were not the same patients as in the JAMA study. Using this definition, we observed that there was no overlap between these cases and the cases included in a previous study. We also referred to it in the results . "None of these cases had been coded in the database as being toxin positive at any time, including in the 30 days before the vancomycin prescription date (index date). " We again mentioned in the discussion " The use of 3 different case definitions for CDAD from a validated research database — laboratory diagnosis based on a positive toxin assay result (n = 833), physician diagnosis (n = 400) and receipt of a prescription for oral vancomycin therapy (n = 317) — yielded similar proportions of patients with prior proton pump inhibitor exposure (24%, 21%1 and 19%). The proportion of patients who had previously been exposed to antibiotics was higher among cases defined on the basis of vancomycin treatment (55%) than among those defined on the basis of a positive toxin assay result (34%) or physician diagnosis (38%). Conflict of Interest:None declared |
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Adam D Porath Renown Regional Medical Center
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aporath{at}renown.org Adam D Porath
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I read with great interest the article by Dial et al. which reported an increased risk of CDAD with exposure to proton pump inhibitors.1 Cases for this study were obtained from the United Kingdom General Practice Research Database (GPRD) between the dates of Jan. 1, 1994 and Dec. 31, 2004. The authors claim that no overlap in patients was observed between this study and a previous study.2 Interestingly, in the previous study conducted by Dial et al., data was also derived from the GPRD between Jan 1,1994 and Dec. 31, 2004. Case patients in this study were identified as those with a first occurrence of CDAD based on a positive C. difficile toxin assay and/or a clinical diagnosis from their general practitioner. I am interested to learn how it is possible that the patients identified in the current study are not those previously studied. It seems very likely that any patient treated with oral vancomycin in the current study would have either had a positive C. difficile toxin result or would have received a clinical diagnosis of CDAD during the study period. Adam Porath Pharmacy Practice Resident, Department of Pharmacy, Renown Regional Medical Center, Reno, Nevada, United States of America References 1. Dial S, Delaney JAC, Scheider V, et al. Proton pump inhibitor use and risk of community-acquired Clostridium difficile-associated disease defined by prescription for oral vancomycin. CMAJ 2006;175(7):745-8. 2. Dial S, Delaney JAC, Barkun AN, et al. Use of gastric acid-suppressive agents and the risk of community-acquired Clostridium difficile-associated disease. JAMA 2005;294:2989-95. Conflict of Interest:None declared |
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