Evaluation of an adenosine deaminase (ADA) assay in serum, pleural, pericardial, peritoneal, and cerebrospinal fluids on the Roche cobas c501 analyzer.

OBJECTIVES

Adenosine deaminase (ADA) can be increased in various body fluids during infectious and inflammatory states. The objective of this study was to evaluate the performance characteristics of the Diazyme ADA assay for serum, pleural, pericardial, peritoneal, and cerebrospinal fluids using the Roche cobas c501 analyzer.

METHODS

Accuracy, linearity, recovery, precision, sensitivity, specificity, reference interval, and stability studies were conducted. Potential interference of hyaluronidase and ultracentrifugation pre-treatment for viscosity on ADA concentrations were further evaluated.

RESULTS

Assay method comparison to two separate external laboratories showed the following results (slope, intercept, %bias): serum (1.053, -0.478, 4.4 %); pleural (1.046, -1.41, 2.6 %). Accuracy (109.6 % recovery) was further demonstrated using a commercially available ADA reference material (BCR647). Linearity and spiked recovery studies showed percent recoveries ranging 94.3-109.3 %. Precision across all specimen types was ≤4.7 %CV. Interference was observed with increasing concentrations of various sources of conjugated and unconjugated bilirubin. Reference intervals were established for serum and pleural fluids, and previously published reference intervals were verified for pericardial, peritoneal, and cerebrospinal fluids. All specimen types were stable for 24 h ambient (8-25 °C), 1 week refrigerated (2-8 °C), and 1 month frozen (-20 °C). Of the two types of hyaluronidase evaluated, one showed positive interference for ADA (Sigma-Aldrich, H3506; 4.59 to 17.90 average % difference from baseline). Ultracentrifugation did not interfere with results (-2.32 to 0.87 average % difference from baseline).

CONCLUSIONS

The Diazyme ADA assay was validated for use in our laboratory for all fluid types evaluated. Interference was observed with increasing concentrations of bilirubin and one source of hyaluronidase.