Table. Clinical and laboratory characteristics of patients suspected of having false-positive cultures for Mycobacterium tuberculosis^a.

Patient	Lab	Specimen type	Initial or follow-up specimen	Sputum smear result	Clinical signs and symptoms	Comments	Panel decision	Final diagnosis
1	1	Sputum	Initial	Negative	36-yr-old man with AIDS hospitalized with cough, dyspnea, right lower lobe infiltrate; he improved with trimethoprim and sulfamethoxazole alone	Genotype of isolate matched that of another patient whose specimen was processed same day	Cross-contamination	Bacterial pneumonia
2	2	Sputum	Initial	2+ Positive	28-yr-old man with HIV infection with fever, cough, right lower lobe infiltrate; improved with ceftazidime	Genotype of isolate matched that of another patient hospitalized on the same ward	Mislabeled specimen	Bacterial pneumonia
3	2	Sputum	Initial	Negative	31-yr-old woman hospitalized with cough, left lower lobe infiltrate, and leukocytosis; chest radiograph showed improvement with clindamycin and ofloxacin	Genotype of isolate matched that of another patient whose specimen was processed same day	Cross-contamination	Bacterial pneumonia
4	2	Sputum	Initial	Negative	44-yr-old man hospitalized with cough and right lower lobe infiltrate; improved with levofloxacin before anti-TB therapy initiated	Genotype of isolate matched that of another patient whose specimen in the BACTEC instrument immediately preceded the case patient	Cross-contamination	Lung abscess
5	2	Sputum	Follow-up	Negative	68-yr-old woman newly immigrated from China with cough; chest radiograph showed bi-apical fibronodular changes	Genotype of second isolate >30 days later did not match that of initial isolate or any other isolate in database	Mislabeled specimen or mixed infection	Bacterial pneumonia versus TB with mixed infection]
6	2	Sputum	Initial	4+ Positive	82-yr-old man with cough, fever; chest radiograph showed chronically increased right mid-lung interstitial markings	Genotype of isolate matched that of another patient hospitalized on the same ward	Mislabeled specimen or cross-contamination	Bacterial pneumonia
7	2	Sputum	Initial	Negative	27-yr-old woman with upper respiratory symptoms; chest radiograph was normal	Genotype of isolate matched that of another patient whose specimen was processed same day	Cross-contamination	Upper respiratory tract infection
8	2	Sputum	Initial	Negative	44-yr-old man with hemoptysis and known pulmonary metastases of squamous cell carcinoma of trachea; chest radiograph showed three large cavities with air-fluid levels; bronchoscopy culture grew H. influenzae, and patient improved on antibiotics alone	Genotype of isolate matched that of another patient whose specimen was processed same day	Cross-contamination	Lung abscess
9	2	Broncho-alveloar lavage	Initial	Negative	55-yr-old woman hospitalized with dyspnea and left lower lobe infiltrate; she improved with broad-spectrum antibiotics alone	Genotype of isolate matched that of another patient whose specimen was processed same day	Cross-contamination	Bacterial pneumonia
10	3	Sputum	Follow-up	Negative	34-yr-old homeless man with HIV infection, fever, and cervical lymphadenopathy; chest radiograph showed left lung nodule	Genotype of initial isolate matched that of another homeless TB patient; follow-up specimen (35 days later) had a unique genotype	TB	TB

^aLab, laboratory; TB, tuberculosis; H. influenzae, Haemophilus influenzae.