The effect of changes in laboratory practices on the rate of false-positive cultures for Mycobacterium tuberculosis

Citation
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
Journal title
ARCHIVES OF PATHOLOGY & LABORATORY MEDICINE
ISSN journal
0003-9985 → ACNP
Volume
125
Issue
9
Year of publication
2001
Pages
1213 - 1216
Database
ISI
SICI code
0003-9985(200109)125:9<1213:TEOCIL>2.0.ZU;2-I
Abstract
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.