Determination of a Beckman Coulter AU turbidometric method-specific caeruloplasmin reference interval

Abstract

Background Method-dependent variation of caeruloplasmin measurement is significant and necessitates the requirement for assay-specific reference intervals. Local determination becomes necessary in the absence of suitable published or manufacturer-quoted reference intervals. Methods Applicability of the Beckman Coulter AU-quoted reference interval was determined by assay of 20 surplus serum samples from patients attending the medical renal stones clinic at University Hospital Southampton. Subsequently, 60 additional samples were collected for local reference interval determination. Samples were analysed for caeruloplasmin using the Beckman Coulter AU turbidometric kit on an AU680 analyser. Outliers were removed, and non-parametric rank analysis of the results was performed. Results The Beckman Coulter-quoted reference interval of 200–600 mg/L was unsuitable with 40% of the verification samples falling below 200 mg/L. A caeruloplasmin reference interval of 150–320 mg/L was established. Conclusion Users should be aware the quoted Beckman Coulter AU turbidometric reference interval may not be appropriate. We have established a method-specific adult reference interval for routine use.