Tuberculosis in the Workplace (2001) / Chapter Skim
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Appendix B The Tuberculin Skin Test
Appendix B The Tuberculin Skin Test
Pages 179-188
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From page 179... ...
Despite its failure as a therapeutic substance, tuberculin rapidly became an important diagnostic test. Patients who received tuberculin in an attempt to cure them had generalized systemic reactions including fever, muscle aches, and abdominal discomfort with nausea and vomiting.
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From page 180... ...
Despite this demonstration of equal potency, there have been a number of reports suggesting an increase in false-positive reactions in skin testing programs that switched from Tubersol (Connaught, Swiftwater, PA) to Aplisol (Parke-Davis, Morris Plains, NJ)
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From page 181... ...
. This 5-TU dose has become the standard for tuberculin testing in the United States.
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From page 182... ...
The sensitivity of tuberculin testing in patients presenting with newly diagnosed pulmonary tuberculosis is approximately 80 percent.(~7 If) The 20 percent false-negative rate is due to a combination of specific immunosuppression of delayed hypersensitivity from cytokines plus overwhelming acute illness and poor nutrition.
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From page 183... ...
Prior BCG vaccination is generally known, but environmental exposure to other mycobacteria varies widely geographically and is difficult to estimate. The large scale skin-testing surveys in the past have shown a great deal of geographic variability in skin testing results.(~)
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From page 184... ...
A large number of recent studies of serial skin testing programs in hospitals and other medical facilities have shown a clustering of yearly conversion rates around 0.5-1 percent in institutions without obvious exposure to undiagnosed and untreated cases of tuberculosis.(22 23) A1though it is unproveable, it seems a reasonable assumption that these rates of conversion represent the false-positive rate of serial tuberculin testing and that the specificity of the test is 99 to 99.5 percent.
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From page 185... ...
False conversions due to boosting are particularly common in these populations when the second skin test is placed in a serial skin testing program.(25) In order to detect this phenomenon, it is recommended that serial skin testing programs use an initial two-step test in which a second skin test is placed approximately 1-week after the first if there is no reaction to the first and that significant reactions to the second test are considered boosted reactions rather than conversions.
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From page 186... ...
Conversion rates above 2 percent probably represent actual transmission of infection. Implications of Decreased Positive-Predictive Value for Tuberculin Test on a Tuberculosis Program Almost all information concerning interventions in tuberculosis infection without disease are based on studies in populations with a high prevalence of tuberculosis infection and thus a high positive predictive value of the tuberculin skin test.
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From page 187... ...
An atlas of sensitivity to tuberculin, PPD-B, and histoplasmin in the United States. American Review of Respiratory Diseases 1969; 99:1-132.
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From page 188... ...
Choosing an appropriate cutting point for conversion in annual tuberculin skin testing. American Review of Respiratory Diseases 1985; 132:379-381.
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