Pe. Breese et al., The effect of changes in laboratory practices on the rate of false-positive cultures for Mycobacterium tuberculosis, ARCH PATH L, 125(9), 2001, pp. 1213-1216
Citations number
14
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Research/Laboratory Medicine & Medical Tecnology","Medical Research Diagnosis & Treatment
Context.-False-positive cultures for Mycobacterium tuberculosis have been f
ound in nearly all DNA fingerprinting studies, but the effectiveness of int
erventions to reduce cross-contamination has not been evaluated.
Objective.-To evaluate whether changes in laboratory policies and procedure
s reduced the rate of false-positive cultures.
Design.-Retrospective study of isolates with matching DNA fingerprints.
Setting.-A mycobacteriology laboratory serving an urban tuberculosis contro
l program and public hospital system.
Patients.-All M tuberculosis isolates processed from July 1994 to December
1999.
Methods.-Isolates were fingerprinted using IS6110; pTBN12 was used to finge
rprint isolates having fewer than 6 copies of IS6110. We further evaluated
all patients having only one positive culture whose DNA fingerprint matched
that of another isolate processed in the laboratory within 42 days.
Interventions.-We changed laboratory policy to reduce the number of smear-p
ositive specimens processed and changed laboratory procedures to minimize t
he risk of cross-contamination during batch processing.
Main Outcome Measure.-The rate of false-positive cultures.
Results.-Of 13 940 specimens processed during the study period, 630 (4.5%)
from 184 patients and 48 laboratory proficiency specimens grew M tuberculos
is. There were no cases (0/184) of probable or definite cross-contamination
, compared with the 4% rate (8/199) identified in our previous study (P =.0
08). We also fingerprinted a convenience sample of isolates from other labo
ratories in Denver; 13.6% (3/22) of these were false-positive, a rate simil
ar to the 11.9% rate (5/42) identified for other laboratories in our previo
us study (P =.84).
Conclusions.-Laboratory cross-contamination decreased significantly after r
elatively simple, inexpensive changes in laboratory policies and practices.
Cross-contamination continued to occur in other laboratories in Denver.