Evaluation and operationalization of commercial serum indices quality control material in the clinical laboratory.

BACKGROUND: Evaluation of specimen suitability for downstream analytical testing and identification of potential interferents in the clinical laboratory is critical for the generation of actionable clinical results. Within the clinical laboratory, hemolysis, icterus, and lipemia are commonly assessed spectrophotometrically. While clinical laboratories rely on analyte-specific quality control (QC) materials to monitor test or instrument performance, QC materials evaluating specimen integrity checks are infrequently implemented. METHODS: Using commercially available specimen integrity materials, we evaluated the Bio-Rad Liquichek™ Serum Indices product on Roche cobas® c701 analyzers at a large academic medical center. Target arbitrary values for the hemolysis, icterus, and lipemia QC materials were 200, 20, and 500, respectively. Means, standard deviations (SD), and coefficients of variation (%CV) were established for hemolysis, icterus, lipemia, and non-interfered QCs, and performance was monitored over a 60-day period. RESULTS: Across four c701 instruments, all QC materials performed well, with %CVs ≤ 1.76%, 4.51%, and 3.46% for hemolysis, icterus, and lipemia QC, respectively. CONCLUSIONS: The Bio-Rad Liquichek Serum Indices product can serve as an effective means of monitoring specimen integrity checks in a manner congruous with existing QC programs.

Comparative evaluation of blood collection tubes for clinical chemistry analysis.

BACKGROUND: Routine chemistry testing is typically performed using serum or plasma to assess a patient's clinical status. At our institution, serum is the specimen type used. To reduce processing times, evaluation of plasma-based and rapid serum gel separator tubes was performed. METHODS: We compared the results of routine chemistry analytes collected in serum gel separator tubes (SST), plasma gel separator tubes (PST), rapid serum gel separator tubes (RST), and plasma tubes without gel separators (DGT). Result concordance was assessed at baseline (immediate testing after processing) and up to one week of refrigerated storage. Other parameters assessed were the susceptibility to hemolysis and lipemia interference, and changes in results after re-centrifugation. Percent changes were compared against the SST and evaluated according to established bias thresholds. RESULTS: Total protein and potassium results at baseline in plasma-based tubes had percent changes from the SST that exceeded acceptability thresholds. Stability was significantly shortened for glucose, potassium, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) when collected in the PST as compared to the SST. The RST was the least susceptible to hemolysis and lipemia interferents. Re-centrifugation affected the serum-based analysis of potassium. CONCLUSIONS: Plasma may reduce processing time at the expense of shortened sample stability and may require specimen source-specific reference intervals for potassium and total protein. The RST provides an alternate option to reduce processing time, while maintaining storage stability.

Establishing hemolysis and lipemia acceptance thresholds for clinical chemistry tests.

BACKGROUND: A key component of laboratory medicine is the evaluation of specimen suitability for downstream analytical testing. Accurate identification and characterization of the impact of interferents on clinical chemistry analytes is important for patient care. To empirically assess the influence of hemolysis and lipemia on clinical chemistry tests analyzed on a Roche cobas® c701 system, we evaluated serum pools spiked with increasing concentrations of hemolysate and Intralipid®. METHODS: Using an interferent acceptance threshold of within ± 10% of the non-hemolyzed or non-lipemic results, 31 routine chemistry analytes were evaluated. RESULTS: The majority of analytes were determined to have the same or very similar acceptability thresholds as those listed in the vendor package insert. However, several analytes resulted in new thresholds that deviated from manufacturer recommendations (9 higher and 2 lower for lipemia, 7 higher and 6 lower for hemolysis). Samples with high enzyme activities (LDH, ALT, AST, ALP, and CK) were observed to tolerate higher levels of hemolysis, and tiered hemolysis thresholds were established for these enzymes. Independent evaluation of indices is recommended to enable thoughtful implementation of specimen quality criteria and to provide guidance to laboratorians and providers on the nature of these interferences.