Clinical Impact of Nucleic Acid Amplification Testing in the Diagnosis of Mycobacterium Tuberculosis: A 10-Year Longitudinal Study

The Use of Xpert MTB/RIF Ultra Testing for Early Diagnosis of Tuberculosis: A Retrospective Study from a Single-Center Database

Tuberculosis (TB) is a multisystemic contagious disease produced by Mycobacterium tuberculosis complex bacteria (MTBC), with a prevalence of 65:100,000 inhabitants in Romania (six times higher than the European average). The diagnosis usually relies on the detection of MTBC in culture. Although this is a sensitive method of detection and remains the "gold standard", the results are obtained after several weeks. Nucleic acid amplification tests (NAATs), being a quick and sensitive method, represent progress in the diagnosis of TB. The aim of this study is to assess the assumption that NAAT using Xpert MTB/RIF is an efficient method of TB diagnosis and has the capacity to reduce false-positive results. Pathological samples from 862 patients with TB suspicion were tested using microscopic examination, molecular testing and bacterial culture. The results show that the Xpert MTB/RIF Ultra test has a sensitivity of 95% and a specificity of 96.4% compared with 54.8% sensitivity and 99.5% specificity for Ziehl-Neelsen stain microscopy, and an average of 30 days gained in the diagnosis of TB compared with bacterial culture. The implementation of molecular testing in TB laboratories leads to an important increase in early diagnostics of the disease and the prompter isolation and treatment of infected patients.

Delays in Isolating Patients Admitted to Hospital with Pulmonary Tuberculosis in Korea

BACKGROUND

Delays in isolating patients admitted to hospital with active pulmonary tuberculosis (PTB) can contribute to nosocomial transmission; however, in Korea, patients with clinically diagnosed PTB are not routinely isolated while awaiting microbiological confirmation of the diagnosis. We aimed to assess the extent of delays in isolating patients admitted with PTB and to identify the factors associated with delayed isolation.

METHODS

We retrospectively reviewed the electronic medical records of patients aged ≥ 18 years with active PTB, between January 2008 and December 2017, from two Korean hospitals.

RESULTS

Among 1,062 patients, 612 (57.6%) were not isolated on admission day. The median time from admission to isolation was 1 day (interquartile range: 0-2 days). The independent risk factor most strongly associated with delayed isolation was admission to departments other than pulmonology or infectious diseases departments (adjusted odds ratio [aOR], 5.302; 95% confidence interval [CI], 3.177-8.847; P < 0.001). Factors associated with isolation on admission day were a past history of tuberculosis (TB) (aOR, 0.669; 95% CI, 0.494-0.906; P = 0.009), night sweats (aOR, 0.530; 95% CI, 0.330-0.851; P = 0.009), and apical infiltrates on chest radiographs (aOR, 0.452; 95% CI, 0.276-0.740; P = 0.002).

CONCLUSION

Concerning patients subsequently diagnosed with active PTB, > 50% were not isolated on admission day. We suggest that the patients with clinically suspected PTB including the elderly who have a past history of TB, night sweats, or apical infiltration on chest radiographs, be presumptively isolated on admission, without waiting for microbiological confirmation of the diagnosis.

Impact of nucleic acid amplification test on pulmonary tuberculosis notifications and treatments in Taiwan: a 7-year single-center cohort study

Background

Nucleic acid amplification tests (NAAT) have been used as a diagnostic tool for pulmonary tuberculosis (PTB) in Taiwan for many years. In accordance with Taiwanese legislation, health care personnel are required to notify the Centers for Disease Control and Prevention (CDC) in case of suspected PTB. This study aimed to investigate the impact of NAAT(Gen-Probe) on the notification system for PTB and anti-tuberculosis treatments in Taiwan.

Methods

A retrospective study on the impact of NAAT (Enhanced Amplified Mycobacterium tuberculosis Direct Test [E-MTD], Gen-Probe, San Diego, CA, USA) [NAAT(Gen-Probe)] was carried out at Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation from March 2011 to December 2017. During the study period, microscopic acid-fast-bacilli smears and mycobacterial cultures were available for PTB diagnosis. NAAT(Gen-Probe) was first introduced at the hospital in January 2014 for use as a diagnostic method for PTB. Positive sputum culture was considered as the gold standard for PTB diagnosis. We excluded clinically-diagnosed PTB cases.

Results

When NAAT(Gen-Probe) was applied, the rate of error notification to CDC decreased from 64.3 to 7.0% (P < 0.001), and unnecessary anti-TB treatments administered to suspected cases decreased from 14.9 to 6.5% (P = 0.005). In the non-PTB group, the mean duration of unnecessary anti-TB treatments changed from 38.9 ± 38.3 days to 37.0 ± 37.9 days (P = 0.874). In the PTB group, the mean time from notifying CDC to initiating treatment decreased from 3.05 ± 6.95 days to 1.48 ± 1.99 days (P = 0.004). The sensitivity, specificity, positive predictive value, and negative predictive value of NAAT(Gen-Probe) were 99.0, 92.3, 99.0, and 92.3%, respectively.

Conclusions

Use of NAAT(Gen-Probe) led to decrease in the rate of error notification of suspected PTB cases to the CDC, avoidance of unnecessary use of anti-TB treatments, and accelerated initiation of appropriate treatments.