To compare resource use by diagnostic outcome among hospital admissions during which tuberculosis (TB) was suspected.

Retrospective study based on chart review and microbiology laboratory data.

The department of medicine in a municipal hospital serving central Brooklyn, New York.

We identified all adult admissions in 1993 during which TB was suspected. We assigned each admission to one of four mutually exclusive groups defined by the results of microbiological tests (acid-fast bacilli [AFB] smear and culture): culture-positive and smear-positive (C + S +); culture-positive and smear-negative (C + S−); culture-negative and smear-positive (C−S+); or culture-negative and smear-negative (C−S−). Each admission was divided into two separate periods to which the utilization of medical resources was assigned: the diagnostic and the postdiagnostic periods, which were separated by the date of receipt of the first definitive culture report.

Data on 519 admissions (93 C+S+; 57 C+S−; 30 C−S+; and 339 C−S−) were analyzed. Although C+S+ were more likely than other groups to have an admitting diagnosis of TB, approximately one quarter of the admissions without TB (C−S+, C−S−) were admitted with the principal diagnosis of TB. For the four groups, C+S+, C+S−, C−S+, and C−S−, the respective rates of TB isolation and anti-TB treatment, and median lengths of isolation were 98%, 87%, and 34 days; 74%, 74%, and 7 days; 83%, 83%, and 15 days; and 44%, 29%, and 0 days. During the diagnostic period, the rate and length of isolation were similar in the AFB-smear—positive groups (C+S+ and C−S+). We estimated that admissions without culture-proven TB (C−S+ and C−S−) accounted for 3,174 (36%) of the 8,712 days of TB isolation expended and for 65% of the 16,671 days of anti-TB treatment. The vast majority of this resource consumption (2,737 [86%] of 3,174 days of isolation) occurred during the diagnostic period before a definitive culture result was known.

Our results suggest that prolonged diagnostic uncertainty and misclassification of cases due to false-positive and false-negative smears are associated with substantial medical-resource consumption. New diagnostic modalities that reduce the period of diagnostic uncertainty could reduce the utilization of resources later found to be unnecessary