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In the article by Krishnan et al published in the August 2007 issue of Arthritis Care & Research (formerly cited as Arthritis Rheum) (pp. 1038–42), the authors used data from the Nationwide Inpatient Sample (NIS), a large, restricted-access, publicly available dataset that is maintained by the Agency for Healthcare Research and Quality (AHRQ). One of the provisions of the NIS Data Use Agreement is that no data observation involving less than or equal to 10 observations is to be published. This measure was put in place by AHRQ to protect individual patients' privacy and to prevent the potential disclosure of personal information. In the article by Krishnan et al, there are some tabulated cells in Tables 1 and 2 that are in violation of this provision. This represents an inadvertent failure by the authors to comply with the Data Use Agreement. Although the authors are confident that nothing in the article could be used to identify individuals or their personal information, the fact remains that the disclosures are in violation of the AHRQ guidelines. The corrected versions of Tables 1 and 2 are shown, the authors request that these corrected versions be cited.

Table 1. Frequency of hip and knee arthroplasties in the Nationwide Inpatient Sample 1993–2002
 HipKnee
NonelectiveElectiveTotalNonelectiveElectiveTotal
Nonagenarians30,3193,65633,9754881,5622,050
Centenarians64633679<10<10<10
Total30,9653,68934,6544921,5652,057
Table 2. In-hospital mortality rates and adjusted mortality risk: a comparison of centenarians and nonagenarians*
 NonagenariansCentenarians
No. of hospitalizationsNo. of deaths (percentage died in hospital)Mortality rate (95% CI)No. of hospitalizationsNo. of deaths (percentage died in hospital)Mortality rate (95% CI)Risk-adjusted hazards ratio (95% CI)
  • *

    95% CI = 95% confidence interval; NA = not applicable.

  • Mortality risk for in-hospital death for centenarians compared with nonagenarians was calculated by Cox regression models where the covariates adjusted for were congestive heart failure, anemia, renal failure diabetes, chronic lung diseases, and hypertension.

All causes1.6 million149,183 (9.1)4.50 (4.47–4.52)41,3355,033 (12.2)6.1 (5.9–6.3)1.36 (1.32–1.40)
Knee arthroplasty2,05226 (1.3)0.8 (0.6–1.2)<100.0 (0.0)0.0NA
Hip arthroplasty33,8511,597 (4.7)2.3 (2.2–2.4)67845 (66)3.2 (2.4–4.3)1.45 (1.10–1.95)

We regret the error.