Black/white differences in leukocyte subpopulations in men.

BACKGROUND: Although counts of leukocytes differ substantially between blacks and whites, and are predictive of ischaemic heart disease (IHD), racial differences in counts of leukocyte subpopulations have received less attention. METHODS: We examined black/white differences in leukocyte subpopulations among 3467 white and 493 black 31-45 year-old-men who had previously served in the US Army. Laboratory determinations were performed at a central location during 1985-1986. RESULTS: Black men had an 840 cell/microliter (or 15%) lower mean total leukocyte count than did white men, largely due to a 960 cell/microliter (or 25%) lower mean neutrophil count. Although black men also had a 20% lower mean monocyte count (= 70 cells/microliter) than did white men, their mean lymphocyte count was 10% higher (approximately = 200 cells/microliter). Counts of various leukocyte subpopulations were associated with cigarette smoking, haemoglobin levels, platelet counts, and several other characteristics, but black/white differences in counts of neutrophils, lymphocytes, monocytes and other subpopulations could not be attributed to any of the examined covariates. CONCLUSIONS: Despite the relatively low counts of leukocytes and neutrophils among black men, their lymphocyte counts are generally higher than those among white men. It is possible that black/white differences in counts of various cell types may influence race-specific rates of IHD, and future studies should attempt to assess the importance of leukocyte subpopulations in the development of clinical disease.

An interlaboratory study of a candidate reference method for platelet counting.

A multinational interlaboratory task force explored the important variables of platelet reference counting and developed a candidate flow cytometric reference method based on the RBC/platelet ratio. A multicenter comparison was performed to determine whether the method met the necessary criteria and was precise enough to be recommended as a new reference method. Each laboratory analyzed serial dilutions of normal specimens, stabilized material, and at least 60 patient specimens with a range of platelet counts from 1 to 400 x 10(3)/microL (1-400 x 10(9)/L). Pooled analysis of the serial dilutions showed that RBC-platelet and RBC-RBC coincidence events became negligible at sufficiently high dilutions (i.e., > 1:1,000). All laboratories demonstrated excellent intra-assay and acceptable interlaboratory precision. Two antibodies (CD61 and CD41) were used for identifying platelets and individually gave acceptable results, but in a minority of samples, staining differences were observed. The optimum method thus uses a double-labeling procedure with a final dilution factor of 1:1,000. The study demonstrated that this method meets the criteria for a reference platelet count.

Guidelines for organisation and management of external quality assessment using proficiency testing. Expert Panel on Cytometry of the International Council for Standardization in Haematology.

This document is intended to assist towards the WHO objective that external quality assessment (EQA) schemes be established at national and/or regional levels world-wide. Quality assurance is defined as all steps taken by the director of a laboratory to ensure reliability of laboratory results and to increase accuracy, reproducibility and between-laboratory comparability. This includes the use of internal quality control procedures and participation in external quality assessment. Internal quality control provides the means for evaluation of analytic test results at the time of testing in order to decide whether they are reliable enough to be released to the requesting clinicians. EQA, on the other hand, refers to a system of retrospective and objective comparison of results from different laboratories by means of proficiency testing (PT) organised by an external agency. The main purpose is to establish between-laboratory and between-method (including between-instrument) comparability, and agreement with a reference standard where one exists. Internal quality control and EQA complement each other and must never be considered as alternatives.

Quality control in haemoglobinometry with special reference to the stability of haemiglobincyanide reference solutions.

In haemoglobinometry grave errors are still being made even though an internationally accepted standardized method is available for the determination of the haemoglobin content of blood. Up to the present only haemiglobincyanide reference solutions have been available on a wide scale to check the measuring stage of the standardized haemiglobincyanide method. These reference solutions are shown to remain stable, under proper storage conditions, for more than 10 years. Concentrated haemoglobin solutions have become available recently, offering the possibility to control the dilution and conversion steps of the haemiglobincyanide method. Such a solution is shown to remain stable, under proper storage conditions, for at least a year. Using both haemiglobincyanide reference solutions and concentrated haemoglobin solutions, as well as having the possibility of checking the cyanide content of the reagent used, an acceptable intra-laboratory control program may now be set up.

Immunobiologics and drugs available from the Centers for Disease Control.

The CDC provides to the medical profession various drugs and immunobiological materials, many of which are investigational. The products available at CDC have changed over the years to meet the changing needs of the American public. Availability of the investigational drugs and immunobiologics permits treatment of patients with diseases against which no FDA-approved drug or treatment is effective and permits research and development of new drugs by manufacturers.

The international system of units (SI) in historical perspective.

American medical journals are shifting to selected SI (Système International d'Unités) units for reporting measurements. Limitation of SI units deemed suitable for use in reporting clinical laboratory results stems from recommendations put forth by the International Federation of Clinical Chemistry and the International Union of Pure and Applied Chemistry. Limitations are: 1) the liter as sole recommended unit of volume in concentration measurement; 2) substance concentration (unit mole) favored over mass concentration (submultiples of the kilogram); and 3) discouraging the use of the prefixes hecto-, deca-, deci-, and centi-. Further discussion by the American Medical Association and other organizations is required before consensus in the US medical community can be reached as to extent of and time frame for conversion to SI for reporting clinical laboratory measurements.

Reference values for the total and differential leukocyte count.

Since 1971, the National Health and Nutrition Examination Surveys have collected data on white blood cell counts and on white cell differential counts that are valid for the U.S. population. This article discusses the validity of the differential counts that result from the availability of a set of reference values for all cell types.

Observations on the alkaline haematin/detergent complex proposed for measuring haemoglobin concentration.

The "alkaline haematin D-575" method for determining haemoglobin, described by Zander et al. [1984) Clin. Chim. Acta 136, 83-93) was tested. Claims that different non-ionic detergents in the reagent result in identical values for the haemoglobin concentration being measured could not be verified. It could also not be verified that a stable end-product with unique spectral characteristics is always reached within approximately 2 min and that conversion of fetal haemoglobin is faster than that with the haemiglobin cyanide method. Because of the many questions regarding the nature and characteristics of the alkaline haematin/detergent complex or complexes, it is not yet possible to recommend this method for routine haemoglobinometry.

Freeze/thaw stability of transferrin, and reference values obtained with kinetic nephelometry.

To determine whether transferrin is stable to repeated freezing and thawing, we used blood specimens from 100 normal adults. Their transferrin concentrations were determined by a laser kinetic nephelometric immunoassay. The sera were stored at 4 degrees C and analyzed the next day (day 1). Specimens 1-25 were stored at -20 degrees C and assayed again on days 3, 4, 8, 16, 22, and 43. Specimens 26-100 were stored at 4 degrees C and analyzed again on day 2. Transferrin proved to be stable to repeated freezing and thawing. Normal reference values with respect to sex and age are given, as determined with the Baker 420 Immunological Nephelometer.

Calibration and control in haemoglobinometry.

In assigning values to fresh blood specimens used for calibrating automated blood cell analysers, haemoglobin concentration should be determined by the ICSH recommended hemiglobincyanide (HiCN) method. Errors in the reference method may be caused by inadequate blood collection, e.g. incorrect anticoagulation; inadequate dilution, e.g. use of inadequately calibrated pipettes; incomplete conversion of haemoglobins to HiCN, e.g. insufficient time for reactions to come to completion; during measurement, e.g. due to turbidity of the HiCN solution to be measured; or by transcription error. Readily available commercial reagent systems and secondary standards are compared with ICSH standards as to their compliance with these standards.

Severe illness in African children with diarrhoea: implications for case management strategies.

To identify clinical disorders associated with severe illness in African children with diarrhoea, we studied a group of under-5-year-olds with diarrhoea who had been brought to a large public hospital in central Cote d'Ivoire. The general condition of children with diarrhoea was assessed and classified according to criteria recommended by WHO, and then used as a nonspecific indicator of severity. Of the 264 children with diarrhoea who were enrolled in the study, 196 had nonsevere illness and 68 severe illness. Children with severe illness were significantly more likely than those with nonsevere illness to be dehydrated (45% versus 11%), moderate-to-severely wasted (47% versus 29%), bacteraemic (26% versus 9%), severely anaemic (haemoglobin level <6 g/dl; 15% versus 6%), have Plasmodium falciparum parasitaemia (27% versus 14%), and have two or more of these five conditions (60% versus 14%). Nontyphoidal Salmonella spp. were present in 68% of the blood isolates but were not associated with seropositivity to human immunodeficiency virus (HIV). The study demonstrates the need for a more comprehensive approach to assessment and management of children with diarrhoea that ensures prompt recognition of bacteraemia, anaemia, wasting and malaria, as well as dehydration. Simple nonspecific observational criteria, such as those recommended by WHO for assessing and classifying general condition, are useful for identifying children with diarrhoea who are at high risk of having life-threatening clinical disorders, and can readily be used by health workers whose clinical training and access to diagnostic laboratory facilities are both limited.

PIP: Researchers prospectively studied 264 children aged less than 5 years with diarrhea who were admitted to the Bouake Regional Hospital Center in the Ivory Coast between June 10 and August 11, 1991, to identify clinical disorders associated with severe diarrhea. They compared data on the 196 children with non-severe diarrhea with data on 68 children with severe diarrhea. All but three of the children were breast fed. The severely ill children were more likely than the non-severely ill children to have dehydration (45% vs. 11%; p 0.01), severe wasting (22% vs. 7%; p 0.01), anemia (29% vs. 13%; p = 0.01), bacteremia (26% vs. 9%; p 0.01), and malarial parasitemia (27% vs. 14%; p = 0.02). 68% of the blood isolates had nontyphoidal Salmonella spp. 6% of children had HIV-1 or HIV-2 infection. The most common pathogens in the stool specimens were rotavirus (41 cases), Campylobacter jejuni (22), Shigella spp. (21), and Salmonella spp (10). These findings indicate a need for a more comprehensive approach to assessment and management of children with diarrhea that secures immediate recognition of bacteremia, anemia, wasting, malaria, and dehydration.

Protocol for evaluation of automated blood cell counters. International Committee for Standardization in Haematology (ICSH).

This protocol is proposed for the evaluation of automated blood cell counters to assess the performance, advantages and limitations of such instruments. It is based on the International Committee for Standardization in Haematology (ICSH) 'Protocol for type testing equipment and apparatus used for haematological analysis' (1978a) and the British Committee for Standardization in Haematology 'Guidelines for the evaluation of instruments used in haematology' (Shinton, England & Kennedy, 1982). The document has been prepared by the ICSH Panel on Cytometry after discussion with colleagues. This tentative protocol will be reviewed 1 year after publication, in accordance with the ICSH rules, before it is adopted as a definitive standard.