B-141 Surprisingly Good Agreement of Siemens and Roche ALT Reference Change Values in Ottawa Hospital Outpatients Distilled from 5 years and 3 years of Siemens and Roche ALT, Respectively

Abstract

Abstract Background Sequential patient data can be transformed into the variable component of the reference change value (RCV) calculation: (CVA2 + CVI2)1/2 (PMID 35137000). We have analyzed sequential healthy and abnormal outpatient ALT to derive RCVs of Ottawa Hospital outpatients (OHOP) who had sequential ALT measured by Siemens or Roche assays. Methods We used the American College of Gastroenterology definition of normal ALT with supplementation of P5P as <25 U/L and <33 U/L in females and males, respectively. We defined abnormal as between the upper limit of normal (ULN) and 3xULN. 5 years of Siemens ALT measurements and subsequently 3 years of Roche ALT were abstracted from the Ottawa Hospital EMR. For the 8 patient cohorts, we tabulated consecutive pairs of intrapatient ALT by time intervals of separation: 0–1 weeks, 1–2 weeks, 2–3 weeks . . ., up to 51–52 weeks. For each interval, we determined the standard deviation of duplicates (SDD) between the paired intrapatient results. SDD was graphed against the midpoints of the weekly interval. Linear regression was used to determine the y-intercept (yo). The 95% RCVs of the male and female, normal and abnormal populations were calculated for the Siemens (with P5P) and Roche (non P5P) assays. Results The Table describes each cohort, yo and RCV. According to the Roche/Siemens cross-over study, Roche ALT values were 10% less than Siemens. This Roche bias is reflected in the normal outpatient ALT means and less so in those with elevated ALT. Also presented are the RCV of low ALT (normal) patients as documented by Ricos and Carobene. Conclusion Our RCVs are realistic: normal ALT patients demonstrate lower RCVs, close to Ricos’ but much larger than Carobene’s which are unachievable due to diurnal variation (over 40% of OHOP ALT are drawn at different times of the day). Furthermore, Carobene’s CVA is tiny.