Variation of CBC Parameters with Storage Time and Temperature

Biswajita Rautaray

Abstract: This study demonstrates that it is possible to perform clinically valid CBC on K2-EDTA anti-coagulated blood 24 hours after collection on refrigerated sample, though not for differential count parameters. On 24-hour sample, MPV and RET %, MCHC should not be considered for diagnosis. HAEMATOCRIT, MCV and RDW consistently elevated with samples age, even at 24 hours, not to be evaluated. After 24 hours WBC, RBC, HGB, PLATELET can be evaluated. Stability of WBC counts up to 24 hours is acceptable for all samples, except EOSINOPHIL (at 4 degree Celsius) counts not stable beyond 24 hours. Altered results obtained in manual differential count, cannot be considered a solution for differential count on aged samples. Most reliable haematological results are obtained from samples analysed same day within 5-8h, soon after collection. When immediate analysis is not possible, sample stability (only CBC parameters except MPV, not differential count) can be prolonged up to 48 hr. on refrigeration. A sample with borderline eosinophil or basophil count stored under refrigeration, still can give report of significant increase in parameters with prolonged storage. Thus refrigeration cant be considered as a solution to prolong storage time in case of blood samples, requiring differential count for clinical diagnosis.

Keywords: CBC variation, Temperature, Time, Aged Sample, Refrigeration