Evaluation of a new reagent for preserving fresh blood samples and its potential usefulness for internal quality controls of multichannel hematology analyzers

We describe a new, easy-to-use reagent, Cyto-Chex (Streck Laboratories, Oma ha, Neb), that preserves fresh whole blood in a non-cross-linking, nonforma lin manner: Target values assigned to fresh blood were essentially met afte r preservation and storage of up to 31 days. Respective mean analytic inacc uracies and short-term intra-assay coefficients of variation (n = 30) were as follows: WBCs, 6.7% and 1.99%; RBCs, 0.7% and 0.76%; hemoglobin, -1.8% a nd 0.79%; hematocrit, -0.3% and 0.75%; mean corpuscular volume, -1.0% and 0 .78%; and platelets, 6.9% and 3.12%. Linearity of dilution-sensitive analyt es was satisfactory over a wide range of dilutions after preservation of bl ood samples. Ten independent laboratories using 10 different instruments de termined day-to-day interassay imprecision during four 7-day periods after blood preservation. Mean interassay coefficients of variation for participa ting laboratories were WBC, 1.92%; RBC, 1.00%; hemoglobin, 1.29%; hematocri t, 2.00%; and platelets 3.29%. Cyto-Chex enables long-term monitoring of in strument accuracy and precision with retained blood specimens of healthy pe rsons. Blood from patient cohorts with various hematologic disorders and wi th a wide range of numeric abnormalities and/or parameter aberrations can b e preserved satisfactorily with this reagent. The reanalysis of preserved p atient blood samples is an important adjunct to the use of commercial contr ol material in quality control programs of multichannel hematology analyzer s.