Utility and Necessity of Repeat Testing of Critical Values in the Clinical Chemistry Laboratory

Abstract

ContextRoutine repeat testing of critical values is a long-standing practice in many clinical laboratories; however, its usefulness and necessity remain to be empirically established and no regulatory requirements yet exist for verification of the critical value results obtained by repeat analysis.ObjectiveTo determine whether repeat testing of critical values is useful and necessary in a clinical chemistry laboratory.MethodsA total of 601 chemistry critical values (potassium, n = 255; sodium, n = 132; calcium, n = 108; glucose, n = 106) obtained from 72,259 routine clinical chemistry specimens were repeat tested. The absolute value and the percentage of difference between the two testing runs were calculated for each of the four critical values and then compared with the allowable error limit put forth in the College of American Pathologists (CAP).ResultsAmong the repeat data for the 601 critical values, a total of 24 showed large differences between the initial result and the repeated result which exceeded the CAP limits for allowable error. The number and rates (%) of large differences for within and outside the analytical measurement range (AMR) were 12 (2.1%) and 12 (41.4%), respectively. For the 572 critical values within the AMR for each test category, the mean absolute difference (mmol/L) and difference(%) between the two testing runs were: potassium, 0.1 mmol/L (2.7%); sodium, 2.1 mmol/L (1.7%); calcium, 0.05 mmol/L (3.0%); glucose, 0.18 mmol/L (2.6%).ConclusionsWhen the initial chemistry critical values are within the AMR, repeated testing does not improve accuracy and is therefore unnecessary. When the initial chemistry critical values are outside the AMR, however, the benefit of repeated testing justifies its performance and makes it necessary. Performing repeat clinical testing on a case-by-case, rather than routine, basis can improve patient care by delivering critical values more rapidly while providing savings on reagent costs associated with unnecessary repeat testing.

Necessity of Routine Repeat Testing of Critical Values in Various Working Shifts

“…Regarding the technical advances in automation and quality management issue in the clinical laboratories over the past decades, routine repeat testing of each critical value have been questioned (10,16).…”

“…Given the attention to patient safety measures and importance of timely reporting of critical results, Vol.15 No.3 Summer 2020 IRANIAN JOURNAL OF PATHOLOGY several issues arose concerning the eligibility of repeating critical values (12). Several studies have been published regarding the utility of repeat critical testing (2,3,8,10,12).…”

Enhance the effectiveness of clinical laboratory critical values initiative notification by implementing a closed‐loop system: A five‐year retrospective observational study

“…19,20 When a measured value triggers its critical value boundaries, the report will change color and a pop-up window will show up in the laboratory information system (LIS) to remind the technician of the generation of critical value. The critical value will be verified before reporting to clinicians, including rechecking the specimen, repeating test, 23 or contacting with clinicians for confirmation. TA B L E 2 (Continued) ratio, and clinician response ratio, are applied for monitoring the whole process of laboratory critical value management.…”

Critical values in hematology of 862 institutions in China

“…However, a survey of CAP Q‐probe showed that routine repeat analysis of automated chemistry and hematology critical values is unlikely to be clinically useful and may adversely affect patient care . Niu et al . concluded that when the initial chemistry critical values are within the analytical measurement range, repeated testing does not improve accuracy and is therefore unnecessary and recommend performing repeat clinical testing on a case‐by‐case basis, rather than routinely.…”