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|Title: ||Identifying ELISPOT and Skin Test Cut-offs for Diagnosis of Mycobacterium Tuberculosis Infection in The Gambia|
|Authors: ||Jeffries, D. J.|
Hill, P. C.
Jackson-Sillah, D. J.
Adegbola, R. A.
Brookes, R. H.
|Keywords: ||PPD skin test|
|Issue Date: ||2006|
|Publisher: ||International Journal of Tuberculosis and Lung Disease (IJTLD)|
|Series/Report no.: ||Vol. 10;No. 2; Pp 192–198|
|Abstract: ||SETTING: An urban area, The Gambia.
OBJECTIVE: To identify ELISPOT and PPD skin test
cut-offs, targeting sensitivity and specificity equivalence.
DESIGN: Tuberculosis cases 15 years of age and their
household contacts underwent ELISPOT, HIV and PPD
skin tests. Cases and contacts sleeping in a different
house were used to estimate sensitivity and specificity,
providing two planes for estimating cut-offs. Specificity
was adjusted for infection from previous exposure using
a multivariate discrimination algorithm.
RESULTS: The point on the line of intersection of the
planes that maximised sensitivity and specificity equivalence
occurred at 4 spots (95% confidence interval [CI]
3.5–5, multiplier 0) for CFP-10 and 5.5 spots (4.5–8,
multiplier 0 for ESAT-6), yielding a sensitivity and
specificity of 76% for both antigens. Combining ESAT-6
and CFP-10 using an ‘or’ statement yielded a maximum
equivalence sensitivity and specificity of 76.5% at 6
spots for ESAT-6 and 11.5 spots for CFP-10. For the
PPD skin test sensitivity and specificity, an equivalence
of 78% occurred at 11 mm induration (9–13 mm).
CONCLUSION: An ELISPOT cut-off for ESAT-6 or CFP-
10 could be set at 4–8 spot forming units (20–40 spots
per million), with little benefit from combining the results.
A cut-off of 9–13 mm for the PPD skin test is reasonable
when comparing with the ELISPOT|
|Appears in Collections:||Medical Laboratory Sciences|
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