Empty iron stores in children and young adults--the diagnostic accuracy of MCV, MCH, and MCHC.

INTRODUCTION: Erythrocyte mean cell volume (MCV) is used clinically to classify anemia, and normal values may be used to exclude iron deficiency. We have studied the diagnostic accuracy of MCV and the related measures mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC) in diagnosing empty iron stores in children and young adults. METHODS: Diagnostic accuracy of MCV, MCH, and MCHC was studied by ROC curve analysis in 6443 ambulant patients aged 0.5-25 years, of which 476 were anemic. In all patients, blood hemoglobin, MCV, MCH, and serum ferritin were measured in specimens sampled at the same time. MCHC was calculated as MCH divided by MCV. The gold standard of empty iron stores was s-ferritin <10, 15, or 20 µg/L. The cutoff limit of MCV giving 90% sensitivity in diagnosing serum ferritin <15 µg/L was constructed using quantile regression. RESULTS: Generally, MCH was slightly more accurate than MCV and MCHC. In the whole study population, the area under the ROC curve was 0.68-0.93 for MCV, 0.73-0.96 for MCH, and 0.68-0.87 for MCHC; and 0.70-0.86, 0.71-0.89, and 0.68-0.88, respectively, in the anemic subpopulation. At the cutoff limits of MCV giving a sensitivity of 90% at all ages in anemic patients, the specificity was about 50%. CONCLUSION: Mean cell hemoglobin, MCH, and MCHC are only moderately accurate in diagnosing empty iron stores in children and young adults, and normal values of these tests do not exclude empty iron stores in anemic patients.

Automated counting of white and red blood cells in the cerebrospinal fluid.

The objective of this study was to examine to what extent the automated method of the Bayer H*2 instrument could replace the visual counting of white and red blood cells in cerebrospinal fluid. The number of white blood cells as well as the percentage of mononuclear and polymorphonuclear cells were counted in the 'Baso channel' (Research screen 3) whereas the number of red cells were registered as the 'R-count' (Research screen 1). All automated cell counts were compared to visual estimates. The automated count yielded reliable results down to 5 x 106 white blood cells/l and 5 x 108 red blood cells/l. In some samples 'noise' was present in the Baso channel. A correct white blood cell count could then be obtained by counting the cells directly as dots on the screen. It was possible to differentiate between polymorphnuclear cells and mononuclear cells at all WBC concentrations. The automated counting of cerebrospinal fluid can be performed without changing thresholds or sample volumes of the instrument. Thus, in the routine practice it will be possible to alternate between automated counting of whole blood samples and cerebrospinal fluid samples.

[Reticulocytes--new possibilities with automated counting]. / Retikulocytter--automatisert telling gir nye muligheter.

A fully automated reticulocyte counter, Sysmex R-1000 has been evaluated at three Norwegian hospitals. The instrument measures fluorescence-labelled RNA in the reticulocytes by flow cytometry. It also generates information on reticulocyte maturity. Instrument precision was superior to that achieved with the routine visual counting method. Samples preserved at room temperature remain stable for one day, whereas samples preserved at 5 degrees C remain stable for four days. An increasing number of reticulocytes is often the first sign of marrow regeneration after bone marrow transplantation or treatment of leukaemia with cytostatica. In patients with chronic renal failure who are receiving erythropoietin, the increase in reticulocytes is seen within days, and precedes the increase in haemoglobin by 2-3 weeks.