Comparison of two commercial quality control sera for adrenocorticotropin (ACTH) used in Elecsys immunoassay system.

OBJECTIVES

The purpose of our study was to investigate whether the storage time and temperature of internal quality control (IQC) material influence the result of ACTH in IQC measurements.

DESIGN AND METHODS

Five levels of IQC materials from two manufacturers were tested through the precision of ACTH, the three freeze/thaw cycles, and the storage time and temperature to evaluate the stability of IQC material. All commercial control materials were simultaneously tested three times a day for five consecutive days.

RESULTS

Total precision of three levels of Bio-Rad IQC sera was 13.93%, 16.45%, and 15.98%, respectively, but repeatability was <2%. The concentration of ACTH decreased by 30%-50% after 3 freeze/thaw cycles. At room temperature, the concentration of ACTH from 3 levels decreased by 16.60%, 17.98%, and 17.20%, respectively, after 0.5 hours, and 70.54%, 74.36%, and 72.03%, respectively, after 4 hours. However, after 2 hours of storage at 4°C, the decline in the measured ACTH IQC was 8.04%, 11.84%, and 10.11%, respectively. Total precision of Roche IQC was 1.17% and 1.08%, respectively. After 3 freeze/thaw cycles, the concentration of ACTH decreased <5%. After 4 hours, the change of ACTH still steadied within 5% both at the room temperature and at 4°C.

CONCLUSION

Roche is a better choice for ACTH of IQC material in Elecsys immunoassay system in our study. If Bio-Rad control materials be used in Elecsys immunoassay system for ACTH IQC testing material, it should be stored at 4°C and testing should be completed within 1 hours.