Evaluation of the HemoCue WBC analyzer to count leucocytes in body fluids

Hemocytometric analysis of body fluids aids in the management and diagnosis of several diseases. Counting of white blood cells (WBC) in synovial fluid discriminates between inflammatory and non-inflammatory forms of joint swelling (1). Differential counting of WBC and erythrocytes (RBC) in cerebrospinal fluid (CSF) forms important and rapid available information in the diagnosis of meningitis, encephalitis and neuroinflammatory diseases like multiple sclerosis. Bacterial peritonitis is suspected when a large number of polymorph nucleated cells (PMN >250 x 106/L) (2) or WBC (WBC >100 x 106/L with ≥50% PMN) (3) are present in ascites and in continuous ambulatory peritoneal dialysis (CAPD) fluid, respectively. Microscopic analysis has been the gold standard for determination of the (differential) WBC and RBC counts in fluids but suffers from high imprecision (4), long turn-around times, and requirement of skilled personnel and mostly is not available 24 hours a day. Automated hemocytometric analysis may be the answer to these problems. Dedicated body-fluid modules have been developed by some manufacturers and are available on two commercial hemocytometers (5, 6). However, these machines are relatively costly and are mostly only available in central laboratory facilities. Moreover, the aspirated volume is relatively large (ca. 130 μL) and the matrix of some fluids such as drain fluids, synovial fluids, and broncheo alveolar lavage (BAL) fluids mostly is complex and not always suitable for automated hemocytometric analysis. Furthermore, no POC-instrument is on the market today to count WBC in body fluids. HemoCue recently launched a very small POC-instrument to count WBC in blood. We investigated whether this POC-analyzer also can be used to count WBC in body fluids.