Latex agglutination test for diagnosing pneumococcal pneumonia in children in developing countries
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K P O'Neill1, N Lloyd-Evans, H Campbell
1Medical Research Council Laboratories, Fajara, The Gambia.
Objective:
To prepare and assess the sensitivity and specificity of a latex agglutination test specific for the serotype of antigen in diagnosing pneumococcal pneumonia in Gambian children.
Design:
Comparison of agglutination test specific for serotype with culture of blood and lung aspirates, countercurrent immunoelectrophoresis, and commercial latex agglutination tests in diagnosing pneumococcal pneumonia. Cross reaction studies and investigation of 102 control children to determine specificity of agglutination test specific for serotype.
Setting:
General medical ward of Medical Research Council laboratories, The Gambia.
Patients:
101 Gambian children aged between 2 months and 10 years admitted with severe pneumonia.
Interventions:
Serum samples were boiled and treated with edetic acid, and urine samples were boiled and concentrated 25 times before testing.
End Point:
A latex agglutination test specific for the serotype of pneumococcal antigen that is sensitive and highly specific for detecting pneumococcus in the urine of patients with pneumococcal pneumonia.
Measurements And Main Results:
Concentrated urine samples from 16 of the 21 children (76%) with pneumococcal pneumonia established by results of culture of blood or lung aspirates gave a positive result with the agglutination test specific for serotype, whereas only four of the 102 urine samples obtained from control children without pneumonia gave positive results. The serotypes of antigens detected in the urine of children with pneumococcal pneumonia and the serotypes of pneumococci isolated from cultures of blood or lung aspirates were the same in all cases.
Conclusions:
When performed on urine samples the agglutination test specific for serotype has a high specificity and is more sensitive than culture of blood or lung aspirates, commercial agglutination tests, or countercurrent immunoelectrophoresis in identifying pneumococcal pneumonia. It is easy to use and should be especially useful in communities with limited laboratory facilities.