Two automated counters, the H1 (Technicon) and the H6000 (Technicon), which count 10,000 cells per sample, were compared and used to examine the clinical relevance of the additional haematological information now provided to the rheumatologist in three groups of patients--38 with rheumatoid arthritis (RA), 41 with ankylosing spondylitis (AS), and 35 with systemic lupus erythematosus (SLE). The two machines agreed in their estimations of the main indices (haemoglobin, red blood cell count, and white blood cell count), but estimations of platelet count and volume were significantly lower on the H6000 machine, as were mean cell haemoglobin and monocyte count, whereas packed cell volume and red cell distribution width were higher. As expected, both machines identified pancytopenia among the group with SLE, while low haemoglobin and high platelet count were found particularly among patients with RA and AS respectively. Additional information available from these counters showed marked variability in red cell size in SLE, and also of haemoglobin content, which is only measured on the newer H1 machine. Flags for microcythaemia, anisochromasis, and white cell noise (usually due to nucleated red cells) were all more common in SLE. Interpretation of results was complicated by the inevitable difference in age and sex distribution among the disease groups, and identification of active disease was also limited by the effect of drugs. In conclusion, the increasingly widespread use of automated counters as part of the routine haematological service may provide the rheumatologist with useful information, but, as always, care should be taken in the interpretation of indices in patients receiving non-steroidal or second line agents, and also in extrapolating results from one machine to another when they are updated or when patients are monitored at more than one centre.
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