The Role of Clinical Suspicion in Evaluating a New Diagnostic Test for Active Tuberculosis
Results of a Multicenter Prospective Trial
- Antonino Catanzaro, MD;
- Sharon Perry, EdM, PhD;
- Jill E. Clarridge, PhD;
- Sherry Dunbar, PhD;
- Sheila Goodnight-White, MD;
- Philip A. LoBue, MD;
- Christopher Peter, PhD;
- Gaby E. Pfyffer, PhD;
- Marcelino F. Sierra, PhD;
- Rainer Weber, MD;
- Gail Woods, MD;
- Greg Mathews;
- Vivian Jonas;
- Katie Smith, PhD;
- Phyllis Della-Latta, MS, PhD
- Author Affiliations: University of California, San Diego Medical Center, San Diego (Drs Catanzaro, Perry, and LoBue); VA Medical Center, Houston, Tex (Drs Clarridge, Dunbar, and Goodnight-White); San Diego County Public Health Laboratory, San Diego (Dr Peter); Swiss National Center for Mycobacteria, Department of Medical Microbiology, University of Zurich, Zurich, Switzerland (Dr Pfyffer); State University of New York, Health Science Center at Brooklyn, Brooklyn, NY (Dr Sierra); Division of Infectious Diseases, University Hospital, Zurich, Switzerland (Dr Weber); Laboratory Medicine, Clinical Microbiology, University of Texas Medical Branch at Galveston (Dr Woods); Gen-Probe Inc, San Diego, Calif (Mr Mathews, Ms Jonas, and Dr Smith); and Pathology Department, Columbia-Presbyterian Medical Center, New York, NY (Dr Della-Latta). Dr Dunbar is now with Luminex, Austin, Tex; Dr LoBue is now with the Centers for Disease Control and Prevention, stationed at the San Diego County Department of Health TB Control Office. Dr Sierra is deceased.
Abstract
Context In laboratory trials, nucleic acid amplification tests for the diagnosis of tuberculosis (TB) are more accurate than acid-fast bacilli (AFB) smear microscopy and are faster than culture. The impact of these tests on clinical diagnosis is not known.
Objective To assess the performance of a nucleic acid amplification test, the enhanced Mycobacterium tuberculosis Direct (E-MTD) test, against a uniform clinical standard stratified by level of clinical suspicion.
Design Prospective multicenter trial conducted between February and December 1996, documenting the clinical suspicion of TB at enrollment and using final comprehensive diagnosis as the criterion standard.
Setting Six urban medical centers and 1 public health TB clinic.
Patients A total of 338 patients with symptoms and signs consistent with active pulmonary TB and complete clinical diagnosis were stratified by the clinical investigators to be at low (≤25%), intermediate (26%-75%), or high (>75%) relative risk of having TB.
Main Outcome Measures Sensitivity, specificity, and positive and negative predictive values of the E-MTD test in clinical suspicion of groups with low (n = 224); intermediate (n = 68); and high (n = 46) clinical suspicion of TB.
Results Based on comprehensive clinical diagnosis, sensitivity of the E-MTD test was 83%, 75%, and 87% for low, intermediate, and high clinical suspicion of TB, respectively, and corresponding specificity was 97%, 100%, and 100% (P = .25). Positive predictive value of the E-MTD test was 59% (low), 100% (intermediate), and 100% (high) compared with 36% (low), 30% (intermediate), and 94% (high) for AFB smear. Corresponding negative predictive values were 99%, 91%, and 91% (E-MTD test) vs 96%, 71%, and 37% (AFB smear).
Conclusions For complex diagnostic problems like TB, clinical risk assessments can provide important information regarding predictive values more likely to be experienced in clinical practice. For this series, a clincial suspicion of TB was helpful in targeting areas of the clinical spectrum in which nucleic acid amplification tests can make an important contribution.
