Utility of gastric aspirates in screening for pulmonary tuberculosis in high risk subjects:The Manitoba experience.

BACKGROUND

Although gastric aspirates (GA) are one of the recommended screening procedures for asymptomatic individuals at high risk for developing tuberculosis (TB), little data exist on the utility of GA for this indication.

OBJECTIVE

To determine the utility of GA as a screening tool in asymptomatic subjects who are at high risk for developing pulmonary TB.

PATIENTS AND METHODS

The study population's clinical, radiographical and Mantoux skin test findings were correlated with a laboratory database of all patients who underwent GA in 1994. Subjects included in the study were those at high risk of developing TB, ie, immigrants placed under surveillance for TB postlanding in Canada (surveillance foreign-born), other foreign-born individuals from high prevalence countries, Status Indians and close contacts of patients with active pulmonary TB.

RESULTS

Four hundred and twelve GAs were performed in 318 patients. Complete data were available in 243 patients. Canadian-born persons who were not Status Indians and foreign-born persons from nonendemic areas (n=37) were excluded. The remaining 206 patients had 261 GAs performed (1.27±0.7 per subject). This group consisted of surveillance foreign-born (n=57), other foreign-born (n=110) and Status Indians (n=39). Fifty-three (26%) were symptomatic and 153 (74%) were asymptomatic. Ninety-eight had a normal chest radiograph, and 108 had an abnormal chest radiograph. Fourteen subjects (26%) in the symptomatic group had Mycobacterium tuberculosis isolated from their GA versus one (0.65%) in the asymptomatic group (P<0.001). One subject (1%) in the normal chest radiograph group versus 14 (12%) in the abnormal chest radiograph group (P=0.005) had M tuberculosis isolated from their GA. Thirty-six subjects were both symptomatic and had abnormal chest radiographs. In this group, 12 (33%) had M tuberculosis isolated from their GA, while none of the patients who were asymptomatic and had normal chest radiographs had a positive M tuberculosis culture. There was no difference in the yield of GA between Mantoux skin test-positive and Mantoux skin test-negative groups.

CONCLUSIONS

GAs have a low yield when used to screen asymptomatic high risk subjects. The results suggest that screening of asymptomatic individuals or those with normal chest radiographs may not be warranted. This will spare many asymptomatic subjects the discomfort of undergoing the procedure and produce a significant cost saving.