RESUMEN
SETTING: Gweru Provincial Hospital, Zimbabwe. OBJECTIVES: To evaluate the accuracy of the diagnosis of pulmonary tuberculosis (PTB) in routine circumstances. DESIGN: Prospective cohort study of routinely diagnosed PTB patients between September 2000 and September 2001. RESULTS: Of 300 patients started on treatment, 161 (53.7%) were positive on direct microscopy. Of the 139 sputum-negative patients, 51 (36.7%) were positive after concentration of specimens, an additional 30 (21.6%) were positive on culture only and 58 (19.3% of the total) were negative for all laboratory investigations. There was no difference in sex, human immunodeficiency virus (HIV) serostatus or treatment outcome between the culture-positive and culture-negative presumed PTB patients. Sputum-negative patients had an increased risk of dying during treatment (RR 2.39, P = 0.015). CONCLUSIONS: The laboratory findings reveal that PTB could be confirmed in more than 80% of patients put on treatment in this setting. The treatment outcomes of the remainder did not differ from those in patients with microbiologically confirmed PTB. In a high HIV-prevalent area, clinicians rightly consider the results of the sputum microscopy test as only one element in the decision making process to put a patient on TB treatment.
Asunto(s)
Infecciones por VIH/epidemiología , Tuberculosis Pulmonar/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Distribución de Chi-Cuadrado , Niño , Preescolar , Femenino , Infecciones por VIH/complicaciones , Humanos , Lactante , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Prospectivos , Esputo/microbiología , Tuberculosis Pulmonar/complicaciones , Tuberculosis Pulmonar/epidemiología , Zimbabwe/epidemiologíaRESUMEN
SETTING: In countries with high human immunodeficiency virus prevalence, laboratory diagnosis of pulmonary tuberculosis with the standard Ziehl-Neelsen (ZN) technique is characterised by low sensitivity. OBJECTIVE: To compare test characteristics of direct microscopy, the concentration method and the Mycobacteria Growth Indicator Tube (MGIT). DESIGN: Three hundred specimens from patients diagnosed with pulmonary tuberculosis were tested for the presence of mycobacteria. Specimens were stained with ZN, decontaminated by adding 4% NaOH, concentrated by centrifuging and processed in MGIT broth. The gold standard was defined as a positive MGIT culture or a positive acid-fast bacilli smear of material obtained from a negative culture after 42 days. RESULTS: A total of 44 (14.7%) specimens were contaminated. Of 256 valid specimens, 234 (91.4%) were positive according to the gold standard definition. Decontamination and concentration of the sample increased the sensitivity of direct microscopy from 67.5% to 87.1%. Specificity remained unchanged (95.5%). The overall median time to detection of MGIT culture-positive specimens was 5 days, ranging from 4 (direct smear-positive specimens) to 12 days (concentration smear-negative specimens). CONCLUSION: The concentration method substantially increases the sensitivity of direct microscopy without much extra input. The MGIT culture technique has considerable advantages, but its relatively high contamination rate and its high cost make it a less recommendable option for widespread use in routine district laboratories.