naats and clinical prediction rules for tb in acute care 1221
hypothetical cohort study design to assess the potential impact of the results of a single NAAT compared to the routine infection control policy for submitting AFB sputum smears of patients admitted to an AIIR for suspected pulmonary TB at county hospitals in Miami9 and San Francisco.10,64 In 2 studies, a single NAAT, either a laboratory-developed test or E-MTD Test,9 and an Xpert assay,10 detected all culture-positive TB patients admitted to an AIIR. However, in 1 study the Xpert assay was negative for an AFB smear-negative, culture-positive TB patient.64 The use of a single NAAT, compared with AFB sputum smear results, had a higher sensitivity (87% vs 76%) and specificity (100% vs 96%) in the study that used the E-MTD test;9 the studies that used the Xpert assay detected identical sensitivity (89% vs 89%10) and similar specificity (100% vs 99%64). In addition, compared to AFB sputum smears, use of a single NAAT was cost-effective and would have decreased utilization of AIIRs from an average of 2.7–1.4 days per patient and would have saved $2,278 per patient or $533,000 annually.10 The use of the Xpert assay on a single concentrated sputum specimen was estimated to have reduced unnecessary respiratory isolation by a median of 35 h (interquartile range, 24–36 h);64 whereas the use of the Xpert assay performed directly on a single unconcentrated sputum specimen reduced unnecessary respiratory isolation by a median of 45 h (interquartile range, 35–46 h).64 A prospective cohort study conducted in a tertiary hospital
in North Carolina compared utilization of AIIRs using the Xpert assay on 1, 2, or 3 respiratory specimens to a strategy using 3 AFB sputumsmears.62 Compared with AIIR use under the 3-AFB sputum smear strategy, the median duration of AIIR use was significantly lower with the strategies using the Xpert assay for the 1, 2, and 3 respiratory specimens, respectively (20.8 h, 41.2 h, 54.0 h, vs 68.0 h).62 However, the 3-AFB sputum smear strategy and the 2- and 3-specimen Xpert strategies detected all 6 TB cases during the study period, whereas the 1-specimen Xpert strategy missed 1 culture- positive TB case in which the first AFB sputum smear was negative.62 The Xpert assay demonstrated sensitivity and specificity similar to those of AFB sputum smears (93% vs 93% and 99% vs 99%, respectively).62 In a retrospective multisite cohort study conducted in
inpatient and outpatient facilities, using NAATs compared to not using NAATs was associated with significant reductions in use of AIIRs as well as reductions in the use of diagnostic procedures such as bronchoscopies and computed tomo- graphy scans and in the initiation of contact investigations for smear-positive, culture-negative suspects.63 Among patients with AFB smear-positive, culture-positive TB, NAATs reduced time to diagnosis of TB.63 In addition, NAATs were noted to significantly reduce duration of TB treatment for both AFB smear-positive and smear-negative patients who did not have TB.63 In other studies, the use of NAATs significantly reduced time to diagnosis and initiation of a treatment regimen for multidrug-resistant TB.65,66 In addition, overtreatment of patients with suspected pulmonary TB67 and exposure time of
healthcare workers to patients with culture-positive pulmonary TB were also significantly reduced.68
Infection Prevention Strategy to Efficiently Isolate and Treat High-Risk Pulmonary TB Patients
The CDC guidelines on prevention of TB transmission in healthcare facilities recommend that airborne infection isola- tion precautions for suspected pulmonary TB be discontinued when contagious TB disease is considered unlikely and either (1) an alternate diagnosis is confirmed that explains the symptoms or (2) the patient has 3 consecutive negative AFB sputum smears.2 The CDC has previously released guidelines for the use of NAATs to diagnose pulmonary TB49 as well as guidelines for use of the Xpert assay.48 Both sets of CDC guidelines48,49 recommend that results for NAATs should be interpreted in the context of AFB sputum smear results and clinical suspicion, and that infectious pulmonary TB disease can be excluded on the basis of microscopy, NAATs, or a combination of these tests, provided that 3 sputum specimens are examined. Also, the collection of at least 3 sputum specimens for culture is recommended to complete the microbiologic evaluation for TB disease.2,48,49 Recently, the FDA extended the indication for use of the
Xpert assay to include testing 1 or 2 sputum specimens as an alternative to the examination of serial AFB smears to aid in the decision to release a patient with presumptive pulmonary TB from an AIIR.13 The expansion of the indication of the Xpert assay was supported by the findings of a multicenter international study that compared a strategy of 1 or 2 Xpert assays to serial AFB sputum smears for initial evaluation of patients with presumptive pulmonary TB.69 Xpert assays using 1 and 2 respiratory specimens detected 97% and 100%, respectively, of AFB smear-positive, culture-positive TB patients.69 Specificities for the 1- and 2-specimen Xpert assay strategy were 99% and 98%, respectively; these specificities were higher than the specificity of 95% for the strategy using 3 AFB smears.69 In addition, the negative predictive value of 1- and 2-specimen Xpert assays was 98% and 99%, respectively, which was higher than a negative predictive value of 93%for the 3-AFB smear strategy.69
proposed combined strategy
We propose an infection prevention strategy (Figures 1 and 2) based on our review of the current epidemiology of TB in the United States, CPRs to detect patients at high risk for culture- positive pulmonary TB, and NAATs for TB detection. This combined strategy aims to identify patients at high risk for pulmonary TB who warrant diagnostic evaluation with an NAAT in an AIIR. The CPR could be used or modified based on local epidemiology to detect patients at high risk for pulmonary TB. In the example CPRs, patients with scores of 4 or greater would be admitted to an AIIR for evaluation for TB and in accordance with the steps in Figure 2, would
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140