1879. Validation of Physician Diagnosis of Bordetella pertussis in Alberta, Canada (2004-2014)
Session: Poster Abstract Session: Vaccines: Pertussis
Saturday, October 10, 2015
Room: Poster Hall
Posters
  • 1879_IDWPOSTER_cmyk_submitted to IDW.pdf (1.0 MB)
  • Background: Pertussis outbreaks are occurring throughout North America.  To assess the utility of physician diagnosis in estimating vaccine effectiveness, we sought to validate physician diagnosis of Bordetella pertussis (BP) against laboratory confirmed cases. Alberta has a universal publicly funded health care insurance system. The Alberta Ministry of Health (AH) captures the ICD-9 coded diagnoses for all physician billing records and hospitalizations. All lab positive and epidemiologically linked cases of notifiable diseases, including BP, are also forwarded to public health within AH. All records include a Unique Lifetime Identifier (ULI) for the patient

    Methods: We used PCR positive cases notified to public health as the gold standard (public health diagnosed). We extracted records with ICD-9 codes of 033, 033.0, 033.1, 033.8, and 033.9 from physician billing and hospitalization databases (physician diagnosed BP). Public health records were deterministically linked with billing and hospitalization data using ULIs. Numbers and proportions of true positive (TP: public health AND physician diagnosed), false positive (FP:  only physician diagnosed) and false negative (FN: only public health diagnosed) cases were estimated. Sensitivity (SE) was calculated as TP/TP+FN; positive predictive value (PPV) as TP/TP+FP. Physician inaccuracy was calculated as FN/TP+FN. Analysis is ongoing as data are received for negative predictive value and specificity.

    Results: From public health OR physician diagnosis 7711 cases of BP were identified. Of these, 13% were TP, 27% FN, and 60% were FP. SE of physician diagnosis was 32.5% (95% CI: 30.9% - 34.1%) and PPV was 18.0% (95% CI: 17.3% – 19.4%). Among 5587 physician diagnosed cases, ICD-9 code 033 (whooping cough) was used in TP and ICD-9 code 033.0 (B. pertussis) was used in FP (86% each). Of the 2124 FN cases 71% were physician diagnosed as “acute respiratory infection” (ICD-9 codes 460-466). Physicians incorrectly diagnosed 67% of public health diagnosed BP cases.

    Conclusion: Our study demonstrates low sensitivity of physician diagnosis for BP. It also shows that 67% of Alberta physician diagnosed cases of BP are misdiagnoses. Additional lab negative data is essential to estimate negative predictive value and specificity.

    Sumana Fathima, BSc1, Kimberley Simmonds, MSc1,2, Steven J. Drews, PhD3,4, Larry Svenson, BSc1,2,5, Margaret L. Russell, MD PhD1 and Canadian Immunization Research Network, (1)Community Health Sciences, University of Calgary, Calgary, AB, Canada, (2)Epidemiology and Surveillance, Alberta Ministry of Health, Edmonton, AB, Canada, (3)Provincial Laboratory for Public Health, Edmonton, AB, Canada, (4)Pathology and Laboratory Medicine, University of Alberta, Edmonton, AB, Canada, (5)School of Public Health, University of Alberta, Edmonton, AB, Canada

    Disclosures:

    S. Fathima, None

    K. Simmonds, None

    S. J. Drews, None

    L. Svenson, None

    M. L. Russell, None

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