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At least 739 records · Page 41Linked to original sources
PubMed1994

Multicenter evaluation of methods for counting residual white cells in leukocyte-depleted red blood cells. The Biomedical Excellence for Safer Transfusion (BEST) Working Party of the International Society of Blood Transfusion.

Two wet workshops were conducted involving 20 laboratories to determine optimum methods for counting residual white blood cells (WBC) in leukocyte-depleted red blood cells (RBC). In both studies, calibration samples containing known concentrations of WBC were prepared by diluting 1-day-old EDTA blood in RBC virtually free of WBC. Study No. 1 was aimed at determining the lower limit of detection and at examining advantages and disadvantages of two methods based on flow cytometry (FC) and on the Nageotte chamber (NC), respectively. This study showed that the lower detection limits for FC and NC were 0.1 and 1 WBC/microliters, respectively. Methods based on FC showed less variability at 0.1-1 WBC/microliters but were equal in performance to counting procedures based on the NC above 1 WBC/microliters. We then designed study No. 2 to evaluate three different protocols using the NC. In protocol 1, samples were diluted 1:10 with Plaxan and with Türk's solution; in protocol 2 a mixture of Türk's solution and Zap-oglobin, a reagent used in manual hemoglobin determinations, was used to dilute the samples 1:5; and protocol 3 involved initial 1:10 dilution of a 1-ml sample with Plaxan followed by WBC concentration into the original 1-ml volume by centrifugation. In each participating laboratory, two technologists independently processed the samples and read the results with an NC. Plaxan and Türk's solution gave comparable results. Interobserver variability was not critical to the results. All three NC methods were valid for counting at concentrations of > or = 1 WBC/microliters.(ABSTRACT TRUNCATED AT 250 WORDS)

Calibration↗
PubMed1996

Multicenter evaluation of the 3% paraformaldehyde method for white cell counting in leukocyte-reduced red blood cells. BEST (Biomedical Excellence for Safer Transfusion) Working Party of the International Society of Blood Transfusion.

BACKGROUND/AIM: The 3% paraformaldehyde (PFA) method is a simple technique for counting residual white blood cells (WBC) in leukocyte-depleted red blood cells (RBC). Preliminary data suggested that its sensitivity is at least equal to PCR and flow cytometry. We report the results of a multicenter study conducted by the BEST Working Party to determine precision and accuracy of the 3% PFA method. STUDY DESIGN: In the 7 participating laboratories, 5 sets of samples containing nominal concentrations of 200, 100, 50, and 10 WBC/ml were prepared by diluting whole blood into 'WBC-free' RBC. Ten milliliters of each sample were processed using the 3% PFA method, which is based on erythrocyte lysis and WBC concentration into 5% of the original sample volume; a Nageotte chamber is used to count concentrated WBC. RESULTS: The precision of the technique varied according to the nominal concentration, ranging from a CV of 12% at 200 WBC/ml to 57% at 10 WBC/ml. The technique measured fewer than the nominal WBC concentrations (mean of all laboratories, -12.4%); underestimation was probably due to cell loss during sample manipulation. Overall accuracy was however acceptable, because statistical considerations establish that the actual WBC concentration would unlikely exceed 2 times the estimated count. CONCLUSIONS: The 3% PFA method is suitable for the enumeration of residual WBC at concentrations > or = 50/ml. It represents a useful tool for evaluation of high performance filters by reference laboratories.

Cell Separation↗
PubMed1990

Guidelines for microplate techniques in liquid-phase blood grouping and antibody screening. A Joint Publication of the British Society for Haematology and the British Blood Transfusion Society. BCSH Blood Transfusion Task Force.

This document is an introduction to microplate serology prepared at a time of very active research and development. Antibody detection techniques are expected to improve during the lifetime of this document. Approximately 25% of hospital blood banks are ABO and D grouping by microplate techniques. Antibody screening by microplate techniques is only being carried out by a small percentage of hospital blood banks but there is likely to be a change to antiglobulin tests by microplate procedures as soon as the methods have been thoroughly tested and approved. There are one or two weak links in these procedures which could give rise to serious errors: (1) Antiglobulin reagents standardized for spin-tube tests may be subject to prozones in liquid phase microplate tests. Each new batch of antiglobulin reagent must be standardized by the microplate procedure in use to show that the reagent is at its optimum anti-IgG dilution for use. However dilutions greater than 1:2 may seriously compromise the anti-complement activity of the reagent. (2) Automated cell washers for microplates are currently under development and should be evaluated by replicate tests with weak anti-D sensitized cells. (3) The combination of diluted anti-IgG and poor washing procedures may lead to neutralization of anti-IgG and cause false negative errors. Future development for improved antiglobulin tests in microplates by a solid phase system is now well advanced and workers proposing to change to antibody screening by microplates are advised to bear this in mind. It is hoped that microplate methodology will move towards standardization based on national guidelines using standard antibody reagents for the validation of new microplate procedures.

ABO Blood-Group System↗