Evaluation of new external quality assessment guidelines involving random blinded rechecking of acid-fast bacilli smears in a pilot project setting in Mexico.
METHODS
Laboratories in Mexico that support the national tuberculosis (TB) control program have been involved in an acid-fast bacilli (AFB) microscopy external quality assurance program which includes rechecking 100% of smears identified as AFB-positive by the local laboratories and 10% of smears identified as AFB-negative. Very few errors have been detected in Mexico using non-random selection and unblinded rechecking of the slides.


OBJECTIVE
To evaluate the results from a 1-year pilot program involving blinded rechecking of randomly selected AFB slides from local TB laboratories in two Mexican states and determine its feasibility for future implementation.


METHODS
To reduce potential bias, laboratory staff from the National TB Laboratory, Institute for Epidemiological Diagnosis and Reference (InDRE), performed quarterly statistical sampling of AFB smears and on-site evaluations in local laboratories in each state. AFB smears were rechecked at the respective state laboratories with discordant results resolved at InDRE.


RESULTS
A significantly greater percentage of errors was detected on the randomly selected, blinded AFB smears than on the non-randomly selected, unblinded smears.


CONCLUSIONS
Random blinded rechecking provides more accurate estimates of AFB microscopy results, resulting in improved diagnosis and monitoring of treatment response.
Martinez
A
A
Instituto de Diagnóstico y Referencia Epidemiológicos, Mexico, DF.
Balandrano
S
S
Parissi
A
A
Zuniga
A
A
Sanchez
M
M
Ridderhof
J
J
Lipman
H B
HB
Madison
B
B
D001431:Bacteriological Techniques / Q000379:methods / Q000592:standards*; D002983:Clinical Competence; D006801:Humans; D066298:In Vitro Techniques; D008800:Mexico; D008853:Microscopy / Q000379:methods / Q000592:standards; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D010865:Pilot Projects; D017410:Practice Guidelines as Topic / Q000592:standards*; D011785:Quality Assurance, Health Care; D013183:Sputum / Q000166:cytology / Q000382:microbiology*; D013597:Systems Analysis; D014397:Tuberculosis, Pulmonary / Q000382:microbiology* / Q000473:pathology