Modification of bioassays for detection of antigens characteristic of bacteria that are causative of ear and respiratory infections to eliminate false positive results caused by nasopharyngeal colonization of children
The present invention relates to modifying rapid immunochromatographic (“ICT”) tests for the detection of characteristic carbohydrate antigens of bacteria that are known to be causative of otitis media and respiratory diseases in children under the age of approximately 12 years. The test modifications involve either (1) reducing the total amount of antibodies to the carbohydrate antigen employed in each test, (2) adding at least one fixed “scrub” line located just prior to the capture line in the sample flow path to the prepared ICT test strip to “scrub” out an identical amount of target antigen from all bodily fluid test samples obtained from both colonized but otherwise healthy children and diseased children, or (3) combinations of (1) and (2).
1. A method for detecting a symptomatic Streptococcus pneumoniae infection in a human subject of age 12 years or less comprising:
applying, to a sample receiving zone at an end of a bibulous test strip, a urine sample obtained from the human subject of age 12 years or less;
allowing the urine sample to flow laterally along the bibulous test strip;
mobilizing tagged purified antibodies capable of binding the C-polysaccharide antigen of Streptococcus pneumoniae , the tagged purified antibodies having been present immediately ahead of the sample receiving zone on the bibulous test strip and rendered flowable by contact with the urine sample, to form a mixture comprising the urine sample and the mobilized tagged purified antibodies;
allowing the binding of the tagged purified antibodies and the C-polysaccharide antigen, to form conjugates of the tagged purified antibodies and the C-polysaccharide antigen in the mixture;
allowing the mixture comprising the conjugates of the tagged purified antibodies and the C-polysaccharide antigen to flow further along the bibulous test strip;
allowing the binding of the conjugates of the tagged purified antibodies and the C-polysaccharide antigen to scrub line antibodies specific for the conjugates of the tagged purified antibodies and the C-polysaccharide antigen, the scrub line antibodies having been immobilized in at least one scrub line along the bibulous test strip;
allowing the mixture comprising the conjugates of the tagged purified antibodies and the C-polysaccharide antigen to flow downstream of the at least one scrub line; and allowing the binding of capture line antibodies specific for the conjugates of the tagged purified antibodies and the C-polysaccharide antigen, the capture line antibodies having been immobilized in a capture line downstream of the at least one scrub line, to the conjugates of the tagged purified antibodies and the C-polysaccharide antigen, wherein color formation in the downstream capture line resulting from the binding of the conjugates of the tagged purified antibodies and the C-polysaccharide antigen to the immobilized capture line antibodies specific for the conjugates of the tagged purified antibodies and the C-polysaccharide antigen is indicative of the symptomatic Streptococcus pneumoniae infection in the subject.