Association of Rapid Molecular Testing With Duration of Respiratory Isolation for Patients With Possible Tuberculosis in a US Hospital

Abstract

Importance: New guidelines recommend that molecular testing replace sputum-smear microscopy to guide discontinuation of respiratory isolation in patients undergoing evaluation for active tuberculosis (TB) in health care settings.

Objective: To evaluate the implementation and impact of a molecular testing strategy to guide discontinuation of isolation.

Design, setting, and participants: Prospective cohort study with a pragmatic, before-and-after-implementation design of 621 consecutive patients hospitalized at Zuckerberg San Francisco General Hospital and Trauma Center who were undergoing sputum examination for evaluation for active pulmonary TB from January 2014 to January 2016.

Interventions: Implementation of a sputum molecular testing algorithm using GeneXpert MTB/RIF (Xpert; Cepheid) to guide discontinuation of isolation.

Main outcomes and measures: We measured the proportion of patients with molecular testing ordered and completed; the accuracy of the molecular testing algorithm in reference to mycobacterial culture; the duration of each component of the testing and isolation processes; length of stay; mean days in isolation and in hospital; and mean cost. We extracted data from hospital records and compared measures before and after implementation.

Results: Clinicians ordered sputum testing for TB for 621 patients at ZSFG during the 2-year study period. Of 301 patients in the preimplementation period with at least 1 sputum microscopy and culture ordered, clinicians completed the rapid TB testing evaluation process for 233 (77%).Among 320 patients evaluated in the postimplementation period, clinicians ordered molecular testing for 234 (73%) patients and received results for 295 of 302 (98%) tests ordered. Median age was 54 years (interquartile range, 44-63 years), and 161 (26%) were women. The molecular testing algorithm accurately diagnosed all 7 patients with culture-confirmed TB and excluded TB in all 251 patients with Mycobacterium tuberculosis (MTB) culture-negative results. Compared with the preimplementation period, there were significant decreases in median times to final rapid test result (39.1 vs 22.4 hours, P < .001), discontinuation of isolation (2.9 vs 2.5 days, P = .001), and hospital discharge (6.0 vs 4.9 days, P = .003), on average saving $13 347 per isolated TB-negative patient.

Conclusions and relevance: A sputum molecular testing algorithm to guide discontinuation of respiratory isolation for patients undergoing evaluation for active TB was safe, feasible, widely and sustainably adopted, and provided substantial clinical and economic benefits. Molecular testing may facilitate more efficient, patient-centered evaluation for possible TB in US hospitals.

Figure 1.. Algorithm incorporating GeneXpert MTB/RIF molecular testing to guide TB evaluation and discontinuation of respiratory isolation.

Legend: This algorithm was disseminated to clinicians and bedside nurses through information sessions, handouts, wall posters, and a website linked in all of these materials and in the electronic order entry system. The algorithm was designed by leaders from Clinical Microbiology, Hospital Infection Control, Nursing, Engineering, Emergency Medicine, HIV Medicine and Infectious Diseases, and Pulmonary Medicine at ZSFG, and the San Francisco Director of TB Control. The clinical probability of a patient having TB was assessed by bedside clinicians. “High-level” airborne infection isolation requires that a patient be placed in a room or tent with a negative-pressure ventilation system. “Low-level” respiratory isolation involves placing a patient in a conventional private room without a negative-pressure ventilation system when no high-level isolation rooms are available and the patient is considered to have a low clinical probability of having highly infectious TB. Homeless patients were deemed to have a lower public health risk based on San Francisco’s robust system for and experience with registering, TB testing, and tracking homeless individuals in homeless shelters in the city. Abbreviations: AFB, acid-fast bacilli; CXR, chest x-ray; cx, mycobacterial culture; d/c, discharge; f/u, follow-up; ZSFG, Zuckerberg San Francisco General Hospital; TB, tuberculosis; TB Control, TB Control Program at the San Francisco Department of Public Health. Xpert, Xpert MTB/RIF.

Figure 2.. Flow diagram describing the TB evaluation process for all participants.

Abbreviations: TB, tuberculosis. Legend: We defined patients with ≤2 sputum smear microscopy results, if negative, as “Rapid TB testing not completed.” In addition, we defined patients with only one Xpert performed, if negative, and no sputum smear microscopy results, as “Rapid TB testing not completed,” in accordance with revised institutional guidelines for discontinuing respiratory isolation(Figure 1). Percentages may not add to 100% due to rounding.