PLASMA CREATININE RESULTS DERIVED FROM AN END-POINT MODIFICATION OF THE JAFFE METHOD

For values in the normal pediatric range, endpoint modifications of th e Jaffe method for measuring plasma creatinine (Pcr) yield higher resu lts than other commonly used techniques. In an effort to evaluate the Olympus AU5000 endpoint method used by the large reference laboratory to which many of our patients are directed by their third-party payor, we compared results with a kinetic Jaffe technique using paired sampl es from the same specimens. In 46 samples, the kinetic method measured Per at less than or equal to 0.8 mg/dl, whereas the endpoint techniqu e Per was higher by 0.1 mg/dl in 6 (13%), 0.2 mg/dl in 23 (50%), and 0 .3 mg/dl in 16 (35%) samples (P<0.0001). The combination of these high er values and the same reported normal range for all children ages 2-1 2 years (0.3-1.0 mg/dl) and 13-17 years (0.7-1.4 mg/dl) makes interpre tation of Olympus AU5000 endpoint method results difficult, particular ly for younger children. The results reinforce the need for each labor atory to provide comprehensive age- and sex-adjusted normal P-Cr range s.