For the most accurate and reproducible hematological results, whole blood specimens should be analyzed as soon as possible after collection.3 With multi-center studies, samples may be drawn off-site and then transported at ambient temperatures to another laboratory.5,11 Transportation times may vary depending on distance and location of the laboratories. Automated hematological analysis of specimens, particularly analysis of the differential count if delayed beyond 4 hours, has in the past yielded doubtful, and often invalid, results. Older technologies most commonly rely upon cell size or cell size together with scatter properties to differentiate white blood cell populations. Because the size and scatter properties of white cells change as a blood sample ages, automated analysis of the differential becomes more unreliable with time. New technologies for the performance of automated differentials have reduced many of the problems associated with automated differential counts dependent on scatter properties only.6,7,9 The properties of red blood cells (RBC) also change with time in stored samples, most notably cell size and the red cell indices related to size. The manufacturer recommends each laboratory establish its own standards of acceptability for results on samples held beyond the optimal time for analysis.12 This study examines the complete blood count (CBC) and differential (Diff) parameters as measured by the Sysmex XT-2000i to determine what changes occur and the validity of the results obtained with aged samples over time. The results will be used to determine what hematological parameters can be reported as clinically valid results if a sample cannot be analyzed in a timely manner. The stability over time of the manual Diff was also evaluated with a small group of samples. The purpose of the limited, additional study is to demonstrate what use, if any, the preparation of a …
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