[Specificity of the Mantoux-reaction to the new tuberculin RT23 in relation to that of previously used PPD-RIVM; a comparative study in hospital staff].
OBJECTIVE
In the Netherlands, an increase in prevalence of tuberculin positivity has been noted since the replacement of the Dutch PPD-RIVM preparation by RT23. This investigation was carried out to assess the specificity of RT23 compared with PPD-RIVM.


METHODS
Comparative.


METHODS
In 90 hospital workers simultaneous tuberculin tests were performed in both forearms with RT23 (Statens Serum Institut, Copenhagen, Denmark; lot number 13751; 2 tuberculin units) and PPD-RIVM (Rijksinstituut voor Volksgezondheid en Milieu, Bilthoven, the Netherlands; lot number 76B; 1 IU), respectively. Sensitivity to atypical mycobacteria (Mycobacterium scrophulaceum, M. avium and M. kansasii) was assessed where differences were > 3 mm.


RESULTS
In two of 73 non-vaccinated subjects, reactions to RT23 were 11 and 15 mm larger than to PPD-RIVM; both showed sensitivity to M. scrophulaceum and M. avium. Five of nine BCG vaccinated subjects showed differences of five to eight mm; in four of these, the reaction to RT23 was larger. Repeat testing in one showed no cross-reactions. The specificity of RT23 compared with PPD-RIVM was 96% (cut-off at 10 mm diameter).


CONCLUSIONS
In a low tuberculosis risk population, tuberculin testing with RT23 yields more positive results than PPD-RIVM. This is probably due to stronger cross-reactivity with atypical mycobacteria of RT23. Decisions on isoniazide prophylaxis should take into account an increased false-positivity rate with RT23.
Cobelens
F G
FG
Afd. Interne Geneeskunde, Academisch Medisch Centrum, Amsterdam. f.g.cobelens@amc.uva
de Boer
H E
HE
D000328:Adult; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009165:Mycobacterium Infections, Nontuberculous / Q000175:diagnosis* / Q000276:immunology; D009162:Mycobacterium avium / Q000276:immunology; D019909:Mycobacterium kansasii / Q000276:immunology; D015359:Mycobacterium scrofulaceum / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D009426:Netherlands; D010564:Personnel, Hospital; D012680:Sensitivity and Specificity; D014373:Tuberculin / Q000276:immunology*; D014374:Tuberculin Test / Q000379:methods*; D014376:Tuberculosis / Q000175:diagnosis*
D014373:Tuberculin