Blood urea nitrogen/creatinine change ratio as a delta check method for dialysis specimens

The delta check is used in clinical laboratories to detect specimen mislabeling or misidentification. However, test results can differ markedly pre-versus post-dialysis, and the delta check in fact typically has little value, as well as being labor intensive. We propose the "blood urea nitrogen/creatinine change ratio" (BCCR) as a new delta check method for dialysis cases. A total of 1,116 specimens with same-day pre- and post-dialysis test results were analyzed. Also, the performance of the BCCR was evaluated by simulating specimen mix-up. Among the 1,116 specimens, the median BCCR was 0.80 and the 2.5th, 25th, 75th, and 97.5th percentiles were 0.62, 0.74. 0.84, and 0.93, respectively. In the simulated misidentification dataset, the median BCCR was 0.79 and the 2.5th, 25th, 75th, and 97.5th percentiles were 0.34, 0.61, 1.02, and 1.77, respectively. When the 2.5th and 97.5th percentile values of the BCCR were set as the upper and lower limits, the delta check detected 61.0% of the simulated misidentified specimens. In summary, the BCCR enables detection of changes in important measures and could reduce the rate of false-positives.