Analytical validation of the modified Westergren method on the automated erythrocyte sedimentation rate analyzer CUBE 30 touch.

OBJECTIVES

Analytical validation of automated erythrocyte sedimentation rate (ESR) analyzers is necessary prior to their implementation into routine practice. Our aim was to perform the analytical validation of the modified Westergren method applied on the CUBE 30 touch analyzer (Diesse, Siena, Italy).

METHODS

Validation included determination of within-run and between-run precision following the Clinical and Laboratory Standards Institute EP15-A3 protocol, comparison with the reference Westergren method, sample stability assessment at both room temperature and 4 °C, after 4, 8 and 24-h storage, and checking the extent of hemolysis and lipemia interference.

RESULTS

Coefficients of variation (CVs) for within-run precision were 5.2% for the normal and 2.6% for the abnormal range, while between-run CVs were 9.4 and 2.2%, respectively. Comparison with the Westergren method (n=191) yielded Spearman's correlation coefficient of 0.93, no constant nor proportional difference [y=0.4 (95% CI: -1.7-1.0) + 1.06 (95% CI: 1.00-1.14)x] and a non-significant mean absolute bias of -2.6 mm (95% CI: -5.3-0.2). Lower comparability was evidenced with increasing ESR values, with both constant and proportional differences for ESR values between 40 and 80 mm, and above 80 mm. Sample stability was not compromised up to 8-h storage both at room temperature (p=0.054) and 4 °C (p=0.421). Hemolysis did not affect ESR measurement up to 1.0 g/L of free hemoglobin (p=0.089), while lipemia index above 5.0 g/L affects the ESR result (p=0.004).

CONCLUSIONS

This study proved that CUBE 30 touch provides reliable ESR measurement and satisfactory comparability with the reference Westergren methods, with minor variation related to methodological differences.