Detection of red blood cell antibodies using bacterial antiglobulins: a new assay [abstract]

OBJECTIVE: To develop an agglutination technique using Staphylococcal protein A (SpA) and Steptococcalprotein G (SpG) to detect human red blood cell antibodies. METHODS: Blood samples were obtained from the National Transfusion Service of Jamaica. SpA, SpG, and anti-IgG, -C3d were commercial preparations. SpA and ApG were incubated with sensitized human red blood cells (RBC) to assess their RBC agglutinating capacity. The Ouchterlony technique was used to determine binding between the bacterial antigens and the IgG in human serum. Polyethyleneglycol (PEG) was used as an agglutination enhancer. Agglutination techniques for a large number of samples were developed, using 96 percent well polystyrene microplates and a microscope for visualizing the agglutination techniques to detect human anti-RBC IgG was compared with the traditional Coombs' test. Sensitivity and specificity were determined. RESULTS: SpA and SpG did not appear to cause agglutination of the red cells sensitized in vivo and in vitro. However, no precipitation bands were formed between human serum and the supernatant obtained after reaction of the sensitized RBC with SpA and SpG (Ouchterlony technique). These results indicated that indeed there was binding of SpA and SpG with the sensitized cells since they were not available for binding with human serum. In additon, SpA and SpG agglutinated the sensitized red blood cells in the presence of the PEG. When compared to the Coombs' test, the following results were obtained with new techniques. For the direct method, sensitivity was 93.8 percent and 95.1 percent for SpA and SpG respectively (n= 81), and specificity was 91.4 percent and 93.5 percent for SpA and SpG, respectivley (n= 93). For the indirect method, sensitivity was 96.3 percent and 97.5 percent for SPA and SpG, respectively (n= 81) and its specificity was 100 percent for both proteins (n= 85). CONCLUSION: Agglutination techniques using SpA and SpG constitute alternative and feasible tests for the detection of human red blood cell antibodies. (AU)

Acute respiratory infections in ambulatory malnourished children: a serological study

We studied the aetiological agents of acute respiratory infections occuring in an ambulatory population of 83 malnourished Jamaican-born children aged 6 to 32 months using serological methods for diagnosis. In 60 percent (38/63) of symptomatic children and in 25 percent (5/20) those without reported disease the following microorganisms were observed: parainfluenza viruses in 15 children, influenza viruses in 12, adenovirus in 10, respiratory syncitial virus in 7 and Mycoplasma pneumoniae in 7 children. The prevalence of the viral infections apparently increased with the severity of malnutrition. (AU)

Dual intradermal testing of Barbadian children with tuberculin and battey bacillus antigen

Nine hundred and eight Barbadian children aged 4 to 8 years were tested simultaneously by intradermal injection of 0.05 g standard tuberculin (PPD-S) and an extract of Mycobacterium intracellulare (Battey bacillus) (PPD-B). Of the total number of children tested, 21.8 percent reacted to both antigens. The reaction to PPD-S was significant in 2.6 percent and to PPD-B in 13.4 percent. In 5.9 percent of the children who reacted to one or both antigens the reactions were of equal size; the reaction to PPD-S was larger in 17.4 percent and to PPD-B in 76 percent. It is concluded that the infection atypical mycobateria is not uncommon in Barbados and that a large number of moderate and reactions to tuberculin are the result of atypical infection. There is evidence that atypical mycobaterial infection protects againsts infection with M. tuberculosis and vice versa. No tuberculous infection was found in the children under four years of age. In the 4 to 5, to 6 to 7 and 7 to 8-year age groups, the age specific infection rates were respectively 1.8 percent, 4.7 percent and 4.6 percent. It is concluded that the policy of administering BCG vaccine to children of 5 years of age should be continued. There is some indication that a number of cases of tuberculosis in Barbados are either not being diagnosed or not being reported (AU)