Users beware! Biological variation in complete blood counts over short time intervals

Background

A complete blood count (CBC) is the most commonly ordered laboratory test for patient diagnosis and treatment. Clinical decisions are often made on the basis of a single result which is rarely repeated. The availability of more rapid tests for CBCs that are accessible and approved for Clinical Laboratory Improvement Amendments (CLIA)-waived use at the point of need increases the likelihood that serial testing may occur over short periods of time. Understanding natural CBC variation in healthy individuals may help clinicians interpret serial test results which may have a range of values.

Objective

We sought to evaluate CBCs from blood drawn over a short time period and assessed in separate, accredited labs to understand biological and laboratory-based variability.