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      We thank Rustagi for his interest in our article. The relationship among colonoscopy volume, specialty, and polyp detection rates is complex, and we have provided further data about the effect of colonoscopy volume separately for each specialty (Table 1). Because of the relatively small number of very high-volume endoscopists in the primary care or surgical specialties, we have combined some specialties in Table 1. These data show relationships among colonoscopy volume and polyp detection, polyp removal, and biopsy rates that are generally similar to those reported in our original article, particularly for gastroenterologists. For example, among the lowest-volume providers, nongastroenterologists had consistently lower polyp detection and removal rates than gastroenterologists.
      Table 1Polyp Detection, Biopsy, and Polyp Removal Rates by Specialty and Colonoscopy Volume
      GastroenterologyGeneral or Colorectal SurgeryFamily or Internal MedicineOther
      Annual colonoscopy volume, by quartile
      Annual colonoscopy volume reflects only the number of outpatient colonoscopies in the 20% sample of Medicare beneficiaries.
       Number of endoscopists
        <33381347792364381
        34-55273660720053
        56-82194817011624
        83-3671265565214
        Polyp diagnosis
       Adjusted odds ratio
      All odds ratios adjusted for clustering of outcomes by provider. Odds ratios also are adjusted for years in practice, site of service, provider rural/urban practice location, patient age, sex, race, Charlson comorbidity score, ZIP-code based median income, colonoscopy indication, and anesthesiologist assistance during the procedure.
      (95% CI)
        <331.01 (0.95-1.07)0.73 (0.69-0.78)0.78 (0.72-0.84)0.75 (0.64-0.88)
        34-551.09 (1.03-1.15)0.83 (0.76-0.90)1.00 (0.88-1.13)1.08 (0.83-1.40)
        56-821.07 (1.01-1.13)0.87 (0.75-1.01)0.99 (0.84-1.17)1.11 (0.80-1.54)
        83-3671.00 (Reference)0.84 (0.70-1.02)1.04 (0.85-1.28)0.88 (0.53-1.46)
        Polyp removal
       Adjusted odds ratio
      All odds ratios adjusted for clustering of outcomes by provider. Odds ratios also are adjusted for years in practice, site of service, provider rural/urban practice location, patient age, sex, race, Charlson comorbidity score, ZIP-code based median income, colonoscopy indication, and anesthesiologist assistance during the procedure.
      (95% CI)
        <331.01 (0.95-1.07)0.74 (0.70-0.78)0.76 (0.71-0.82)0.72 (0.62-0.83)
        34-551.09 (1.03-1.15)0.82 (0.75-0.89)0.97 (0.86-1.11)1.13 (0.87-1.47)
        56-821.06 (1.00-1.12)0.84 (0.72-0.97)1.00 (0.84-1.18)1.14 (0.82-1.57)
        83-3671.00 (Reference)0.73 (0.60-0.88)0.97 (0.80-1.17)0.89 (0.55-1.45)
        Diagnostic biopsy
       Adjusted odds ratio
      All odds ratios adjusted for clustering of outcomes by provider. Odds ratios also are adjusted for years in practice, site of service, provider rural/urban practice location, patient age, sex, race, Charlson comorbidity score, ZIP-code based median income, colonoscopy indication, and anesthesiologist assistance during the procedure.
      (95% CI)
        <331.24 (1.15-1.33)0.86 (0.80-0.92)1.12 (1.03-1.23)0.95 (0.81-1.12)
        34-551.16 (1.08-1.24)0.85 (0.76-0.94)1.13 (0.96-1.33)1.08 (0.78-1.51)
        56-821.11 (1.03-1.19)0.88 (0.72-1.07)0.95 (0.79-1.14)1.09 (0.72-1.67)
        83-3671.00 (Reference)0.65 (0.49-0.87)1.19 (0.95-1.49)1.33 (0.72-2.45)
      CI=confidence interval.
      low asterisk Annual colonoscopy volume reflects only the number of outpatient colonoscopies in the 20% sample of Medicare beneficiaries.
      All odds ratios adjusted for clustering of outcomes by provider. Odds ratios also are adjusted for years in practice, site of service, provider rural/urban practice location, patient age, sex, race, Charlson comorbidity score, ZIP-code based median income, colonoscopy indication, and anesthesiologist assistance during the procedure.
      The relationship between specialty and polyp detection or removal rates for higher-volume providers is somewhat more complicated. For all but the lowest-volume primary care physicians, polyp detection and removal rates were similar to highest-volume gastroenterologists. Among the highest-volume providers, polyp detection and removal rates were lower for surgeons compared with gastroenterologists or primary care physicians. Diagnostic biopsy rates were generally lower for surgeons than gastroenterologists, but not for primary care physicians. However, confidence intervals for these estimates are wide because of the small number of nongastroenterologists with high colonoscopy volume.
      Some of the seemingly contrary relationship among specialty, volume, and polyp detection or removal rates noted by Rustagi may be explained by the differences in distribution of colonoscopy volume across specialty. The highest-volume endoscopists are overwhelmingly gastroenterologists, but specialty is more evenly distributed for lowest-volume providers. Therefore, the results for very high-volume providers are dominated by gastroenterologists, whose overall polyp detection, polyp removal, and biopsy rates are higher than nongastroenterologists. These results highlight the fact that both specialty and colonoscopy volume are important determinants of these colonoscopy outcomes.
      The inverse relationship between polyp detection or removal rates and physician years in practice is surprising, but consistent with prior findings.
      • Kaminski M.F.
      • Regula J.
      • Kraszewska E.
      • et al.
      Quality indicators for colonoscopy and the risk of interval cancer.
      Histological data are not available in the Medicare claims; so we could study only polyp detection rates and not adenoma detection rates. However, others have found that adenoma and polyp detection rates are correlated,
      • Chen S.C.
      • Rex D.K.
      Variable detection of nonadenomatous polyps by individual endoscopists at colonoscopy and correlation with adenoma detection.
      suggesting that the relationship between adenoma detection and physician experience would be similar.
      We agree that further studies are needed to understand the mechanisms by which provider characteristics affect colonoscopy quality. While our results characterize the general relationship between provider characteristics and important colonoscopy outcomes, others have suggested that the individual endoscopist is the critical factor in adenoma detection rates.
      • Chen S.C.
      • Rex D.K.
      Endoscopist can be more powerful than age and male gender in predicting adenoma detection at colonoscopy.
      Therefore, it is important that all endoscopists, regardless of specialty, colonoscopy volume, or years in practice, know their polyp detection rates and take measures to improve the quality of their colonoscopy performance because adenoma detection rates have been shown to be inversely associated with the risk of colorectal cancer after colonoscopy.
      • Kaminski M.F.
      • Regula J.
      • Kraszewska E.
      • et al.
      Quality indicators for colonoscopy and the risk of interval cancer.

      References

        • Kaminski M.F.
        • Regula J.
        • Kraszewska E.
        • et al.
        Quality indicators for colonoscopy and the risk of interval cancer.
        N Engl J Med. 2010; 362: 1795-1803
        • Chen S.C.
        • Rex D.K.
        Variable detection of nonadenomatous polyps by individual endoscopists at colonoscopy and correlation with adenoma detection.
        J Clin Gastroenterol. 2008; 42: 704-707
        • Chen S.C.
        • Rex D.K.
        Endoscopist can be more powerful than age and male gender in predicting adenoma detection at colonoscopy.
        Am J Gastroenterol. 2007; 102: 856-861

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