Determining the utility of creatinine delta checks: A large retrospective analysis

Delta checks are a long-standing practice for identifying errors in the laboratory. However, with the decrease in errors due to laboratory automation, their utility is unclear. The objective of this retrospective analysis was to determine whether establishment of a creatinine delta check would be an effective means for capturing true laboratory error.

All patients with a minimum of two creatinine results during March of 2015 were selected for review (n = 23,410 creatinine results). The lowest % change for a previously confirmed creatinine error in our laboratory was approximately 60%; therefore only results that changed by at least ±60% (n = 254) were reviewed. The etiology of creatinine value change was categorized as laboratory error, pathologic change, or non-pathologic change, based upon chart review.

1.2% (3/254) of reviewed delta checks were determined to reflect 2 instances of true laboratory error that went unrecognized by laboratory staff. 91.3% (232/254) of the delta checks were determined to reflect a pathologic or dialysis-related change in creatinine levels. The remaining 7.5% of delta checks (19/234) were deemed to be non-pathologic changes in creatinine.

This study identified two instances of laboratory error reflected by 3 delta checks (1.2%); the vast majority (91.3%) of creatinine results that changed by ±60% were pathologic or dialysis-related. Thus, establishment of a ±60% delta check for creatinine would overwhelmingly flag true biological change and would not be an efficient means for identifying rare laboratory errors. Clinical laboratories should perform similar retrospective analyses prior to enacting delta checks to determine whether they will effectively capture laboratory error.