Comparison of urea reduction ratio and hematocrit data reported in different data systems: results from the Centers for Medicare & Medicaid Services and the Renal Network Inc.

Background: Urea reduction ratio (URR) and hematocrit values reported on the Centers for Medicare & Medicaid Services (CMS) claims were compared with data from two different databases.

Methods: URRs and hematocrits from two different CMS databases (National Claims History and End-Stage Renal Disease Clinical Performance Measures [CPM] Project) and one Network database (The Renal Network Data System [TRNDS]) were compared for October through December 1998 and December 1998, respectively. A sample of records from the regional database was validated by independent chart review.

Results: Nationally, the percentage of agreement for patients with URRs of 65% or greater and less than 65% was 94% (kappa, 0.81; 95% confidence interval [CI], 0.80 to 0.83); regionally, the percentage of agreement was 95% (kappa, 0.85; 95% CI, 0.84 to 0.86). Nationally, linear regression of hematocrit values from both data sources yielded r(2) congruent with 0.61 each month and r(2) = 0.70 for average values during the 3-month study period. Nationally, the percentage of agreement for patients with hematocrits of 33% or greater and less than 33% was 84% (kappa approximately 0.66) each month. Regionally, linear regression of monthly hematocrit values from both data sources yielded r(2) = 0.66, and percentage of agreement for patients with hematocrits of 33% or greater and less than 33% was 87% (kappa, 0.71; 95% CI, 0.70 to 0.73). Validation of a sample of records in the TRNDS database resulted in 98% agreement for patients with URRs of 65% or greater and less than 65% and 96% agreement for patients with hematocrits of 33% or greater and less than 33%.

Conclusion: Although there is general agreement between clinical variables submitted on the claims and in the CPM Project, some variation exists. Data from either source yield the same information when classifying patients as above or below threshold values.