Search

An analysis of the results of a compulsory proficiency testing programme in immunohaematology is presented. Error rates have been calculated for the determination of ABO and Rh(D) groups, the direct antiglobulin test and antibody detection according to defined criteria. The introduction of proficiency testing has been associated with alterations in error rates for some determinations. An educational programme introduced for laboratories with poor performance has proved effective in improving their results in the proficiency testing programme.

Since April 1975 the proficiency of laboratories in Ontario that perform immunohematology tests has been assessed. While the majority of test samples have required only ABO and Rh(D) typing, others have posed problems. The error rate in uncomplicated ABO typing was 1.3/1,000 in 17,479 tests and that in straightforward Rh(D) grouping, 6.6/1,000 in 17,757 tests. False-negative (36/1,000) and false-positive (1.4/1,000) direct antiglobulin tests occurred. Errors in detection of strong alloantibodies (e.g., anti-D) were 19.7, 10.2 and 5.1/1,000 in three test samples. A2B or A2 cells with anti-A1 in serum were sent out in two surveys; error rates in ABO interpretation were 189 and 52/1,000, respectively. Laboratories also experienced difficulty in interpreting the Rh(D) type of cells with positive antiglobulin tests. These surveys have had several effects: (1) laboratories with poor performance have been identified, (2) patterns of practice have been influenced, (3) areas of ignorance have been identified, and (4) a stimulus has been provided for continuing education in immunohematology.

Fifty-six patients with unexplained lymphocytosis were investigated with a panel of antibodies to lymphocyte surface antigens. In 23 the distribution of cell surface markers suggested reactive lymphocytosis. The remaining 33 patients showed a distribution of cell surface markers that indicated or suggested a diagnosis of B-cell lymphoproliferative disease. Two illustrative case reports show how such studies performed early in the investigation of unexplained lymphocytosis may permit earlier diagnosis of the underlying mechanism.

A proficiency testing program in immunohematology, involving over 240 laboratories, was used to assess the detection of anti-D in six concentrations ranging from 11 to 8,500 ng/mL. Using the indirect antiglobulin test, more than 98% of laboratories reporting detected anti-D at all concentrations. Enzyme and albumin antiglobulin methods as routinely practiced did not clearly increase sensitivity, and the direct agglutination methods used were much less sensitive than indirect antiglobulin methods. If proficiency testing truly reflects performance in practice in Ontario, Canada, the sensitivity of manual indirect antiglobulin methods in routine use for the detection of anti-D appears to meet reasonable expectations of these technics.

An absolute lymphocyte count is included in the routine results provided by most automated blood cell counters, providing a prompt indication of peripheral blood lymphocytosis. Transient lymphocytosis is seen in many acutely ill patients, including those with multiple injuries. We have observed a significantly higher death rate among trauma patients with lymphocytosis at presentation; patients with lymphocytosis, on subsequent assessment of injury, proved to have higher Injury Severity Scores than those without lymphocytosis. Investigation of lymphocyte subsets in nine patients with lymphocytosis showed an increase in T cells, reversal of the CD4:CD8 ratio, and, in seven patients, an increase in "natural killer" cells. The presence of lymphocytosis and its early detection as part of a routine blood count may supply a readily available means of identifying a high-risk trauma patient.