ERRORS IN DIAGNOSIS OF SYPHILIS WITH RAPID PLASMA REAGIN TEST ( RPR )
A post graduate question in Medical Microbiology
Today we almost stopped doing the VDRL test, and the next proposition continues to do with RPR test, if you work with laboratory we get at least 1 in 10 tests may be liable of difference of opinion and error prone , a true problem when we do in Pregnant women who are liable to give false positive results defeating the purpose of doing as lone test to screen for syphilis
Sources of Error
Error can be introduced into test results because of factors such as contamination of rubber bulbs False-positive biological reactions have been reported with cardiolipin type of antigens in the following conditions:
Lupus erythematosus • Rheumatic fever • Vaccinia and viral pneumonia • Pneumococcal pneumonia Pneumococcal pneumonia • Infectious mononucleosis • Infectious hepatitis • Leprosy • Malaria • Rheumatoid arthritis • Pregnancy • Aging individuals
False-negative reactions can result from the following:
Poor technique • Ineffective reagents • Improper rotation A gain, if mechanical rotation is below or above the 95- to 110 –rpm acceptable range, the clumping of the antigen tends to be less intense in procedures with undiluted specimen; thus, some minimal reactions may be missed. In quantitative tests, rotation above 110 rpm tends to produce a decrease in titre, apply approximately one dilution lower.Interpretations to limit errors
A diagnosis of syphilis cannot be made based on a single reactive result without clinical signs and symptoms or history
Testing for Neurosyphilis
The RPR cards should not be used for testing CSF. Little reliance should be placed on cord blood serologic testing testing for syphilis
RPR a useful Prognostic test - It can also be used to check the progress of treatment for active syphilis. After a course of effective antibiotic therapy, your doctor would expect to see the number of antibodies drop, and an RPR test could confirm this.
Today many laboratories are doing both RPR and TPHA tests as routine tests moving away from RPR as lone test with possibilities of Missing the diagnosis with false negatives, and conforming the false positives .
A post graduate question in Medical Microbiology
Today we almost stopped doing the VDRL test, and the next proposition continues to do with RPR test, if you work with laboratory we get at least 1 in 10 tests may be liable of difference of opinion and error prone , a true problem when we do in Pregnant women who are liable to give false positive results defeating the purpose of doing as lone test to screen for syphilis
Sources of Error
Error can be introduced into test results because of factors such as contamination of rubber bulbs False-positive biological reactions have been reported with cardiolipin type of antigens in the following conditions:
Lupus erythematosus • Rheumatic fever • Vaccinia and viral pneumonia • Pneumococcal pneumonia Pneumococcal pneumonia • Infectious mononucleosis • Infectious hepatitis • Leprosy • Malaria • Rheumatoid arthritis • Pregnancy • Aging individuals
False-negative reactions can result from the following:
Poor technique • Ineffective reagents • Improper rotation A gain, if mechanical rotation is below or above the 95- to 110 –rpm acceptable range, the clumping of the antigen tends to be less intense in procedures with undiluted specimen; thus, some minimal reactions may be missed. In quantitative tests, rotation above 110 rpm tends to produce a decrease in titre, apply approximately one dilution lower.Interpretations to limit errors
A diagnosis of syphilis cannot be made based on a single reactive result without clinical signs and symptoms or history
Testing for Neurosyphilis
The RPR cards should not be used for testing CSF. Little reliance should be placed on cord blood serologic testing testing for syphilis
RPR a useful Prognostic test - It can also be used to check the progress of treatment for active syphilis. After a course of effective antibiotic therapy, your doctor would expect to see the number of antibodies drop, and an RPR test could confirm this.
Today many laboratories are doing both RPR and TPHA tests as routine tests moving away from RPR as lone test with possibilities of Missing the diagnosis with false negatives, and conforming the false positives .
Ref -SOURCES OF ERROR IN SEROLOGIC AND IMMUNOLOGIC LAB from web resources
Dr.T.V.Rao MD
Dr.T.V.Rao MD
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