How many sputum specimens are necessary to diagnose pulmonary tuberculosis?

Incremental yield of serial sputum examinations in the diagnosis of pulmonary tuberculosis in Taiwan: Findings of a pragmatic trial

BACKGROUND

Presumptive tuberculosis (TB) cases commonly had two to three sputum examinations in Taiwan. The incremental yield of serial sputum examinations has not been assessed before.

METHODS

In a pragmatic trial, presumptive TB patients with a frontline nucleic acid amplification test (NAAT) were classified as group A. Those without a frontline NAAT were randomized into group B frontline NAAT as intervention, and group C usual care. We investigated expected incremental yields and the number of examinations required for detection of one additional TB case from each serial sputum smear and culture.

RESULTS

Of 6835 presumptive TB cases, 395 (5.8%) were smear positive for acid-fast bacilli, and 195 (2.8%) culture positive for M tuberculosis. The expected incremental yield from a third smear was 3.5% and examination of 1712 (95% credibility interval 586-4706) third smears was required to detected one additional TB case. Sensitivity of one smear with an NAAT in group B was 46.8% (95% confidence interval 32.1%-61.9%), and that of two smears in Group C 40.0% (95% confidence interval 25.7%-55.7%). The expected incremental yield from a third culture was 8.4%, and the number of third cultures required to detect one additional TB case was 394 (95% credibility interval 231-670).

CONCLUSIONS

The incremental yield of the third sputum smear was negligible. It may be reasonable to perform an NAAT, smear and culture on the first specimen and culture alone on the second. The utility of the third serial culture for the detection of additional TB case is debatable.

Spot specimen testing with GeneXpert MTB/RIF results compared to morning specimen in a programmatic setting in Cotonou, Benin

BACKGROUND

The diagnosis of tuberculosis (TB) using smear microscopy has been based on testing two specimens: one spot and one early morning sputa. Recently, the World Health Organization (WHO) has recommended to replace, whenever possible, microscopy with GeneXpert® MTB/RIF performed on a single specimen. However, as the bacterial load is higher in early morning specimens than in spot specimens, one could expect lower sensitivity of GeneXpert® MTB/RIF performed only on spot specimens. In this study, we compared results of GeneXpert® MTB/RIF on spot specimens versus early morning specimens, under programmatic conditions in Cotonou, Benin.

METHODS

From June to September 2018, all sputa received from presumptive TB patients at the Supranational Reference Laboratory for Tuberculosis of Cotonou were included in the study. From each patient, two specimens were collected (one spot and one early morning) and GeneXpert® MTB/RIF was performed on both specimens.

RESULTS

In total, 886 participants were included in the study, of whom 737 provided both sputa and 149 (16.8%) gave only the spot specimen. For the 737 participants who provided both sputa, GeneXpert® MTB/RIF was positive for both specimens in 152 participants; for three participants GeneXpert® MTB/RIF was positive on spot specimen but negative on morning specimen while for another three, the test was positive on morning specimen but negative on spot specimen. The overall percentage of agreement was excellent (99.2%) with a positive and negative percent agreement greater than 98%.

CONCLUSION

For TB diagnosis under programmatic conditions in Cotonou, GeneXpert® MTB/RIF in spot specimens gave similar results with the test in morning specimens. Performing GeneXpert® MTB/RIF in both specimens did not significantly increase the number of cases detected. To avoid losing patients from the diagnostic cascade, it is preferable to test sputa produced at the time of the first visit at the health center.

Of tuberculosis and non-tuberculous mycobacterial infections - a comparative analysis of epidemiology, diagnosis and treatment

Pulmonary diseases due to mycobacteria cause significant morbidity and mortality to human health. In addition to tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), recent epidemiological studies have shown the emergence of non-tuberculous mycobacteria (NTM) species in causing lung diseases in humans. Although more than 170 NTM species are present in various environmental niches, only a handful, primarily Mycobacterium avium complex and M. abscessus, have been implicated in pulmonary disease. While TB is transmitted through inhalation of aerosol droplets containing Mtb, generated by patients with symptomatic disease, NTM disease is mostly disseminated through aerosols originated from the environment. However, following inhalation, both Mtb and NTM are phagocytosed by alveolar macrophages in the lungs. Subsequently, various immune cells are recruited from the circulation to the site of infection, which leads to granuloma formation. Although the pathophysiology of TB and NTM diseases share several fundamental cellular and molecular events, the host-susceptibility to Mtb and NTM infections are different. Striking differences also exist in the disease presentation between TB and NTM cases. While NTM disease is primarily associated with bronchiectasis, this condition is rarely a predisposing factor for TB. Similarly, in Human Immunodeficiency Virus (HIV)-infected individuals, NTM disease presents as disseminated, extrapulmonary form rather than as a miliary, pulmonary disease, which is seen in Mtb infection. The diagnostic modalities for TB, including molecular diagnosis and drug-susceptibility testing (DST), are more advanced and possess a higher rate of sensitivity and specificity, compared to the tools available for NTM infections. In general, drug-sensitive TB is effectively treated with a standard multi-drug regimen containing well-defined first- and second-line antibiotics. However, the treatment of drug-resistant TB requires the additional, newer class of antibiotics in combination with or without the first and second-line drugs. In contrast, the NTM species display significant heterogeneity in their susceptibility to standard anti-TB drugs. Thus, the treatment for NTM diseases usually involves the use of macrolides and injectable aminoglycosides. Although well-established international guidelines are available, treatment of NTM disease is mostly empirical and not entirely successful. In general, the treatment duration is much longer for NTM diseases, compared to TB, and resection surgery of affected organ(s) is part of treatment for patients with NTM diseases that do not respond to the antibiotics treatment. Here, we discuss the epidemiology, diagnosis, and treatment modalities available for TB and NTM diseases of humans.

Risk factors of delayed isolation of patients with pulmonary tuberculosis

OBJECTIVES

The aim was to examine the rate of delayed or no isolation of hospitalized patients with pulmonary tuberculosis (TB) and the causes for isolation failure.

METHODS

This retrospective study included patients with pulmonary TB at a university-affiliated hospital in South Korea between January 2015 and June 2018 after excluding those with a stay ≤2 days and those who only visited the emergency department. Patients who were not isolated for ≥3 days were classified as the delayed or no isolation group. We compared the clinical findings and diagnostic test results, between patients managed with delayed or no isolation (D-isolation) and timely isolation (T-isolation).

RESULTS

Of 486 patients with pulmonary TB, 222 patients were included. In 106 cases (47.7%), isolation was delayed or not applied, while in 116 cases, isolation was applied in a timely manner. Typical findings of TB were seen on the chest X-rays of 87 (75.0%) patients in the T-isolation group versus 25 (23.6%) patients in the D-isolation group (p < 0.001). Other factors significantly associated with delayed or no isolation on univariate analyses were older age, admission route (emergency room vs. other), admitting department, negative acid-fast bacilli (AFB) stain, and negative MTB PCR. On multivariate analysis, admission through an outpatient clinic, admission to a department other than infectious diseases or pulmonology, an atypical chest X-ray finding and negative sputum AFB stains were risk factors for isolation failure.

DISCUSSION

Delayed or no isolation of patients with pulmonary TB was attributed mainly to atypical radiological findings and negative findings of direct TB diagnostic tests.

Pulmonary Tuberculosis: Role of Radiology in Diagnosis and Management

Tuberculosis is a public health problem worldwide, including in the United States-particularly among immunocompromised patients and other high-risk groups. Tuberculosis manifests in active and latent forms. Active disease can occur as primary tuberculosis, developing shortly after infection, or postprimary tuberculosis, developing after a long period of latent infection. Primary tuberculosis occurs most commonly in children and immunocompromised patients, who present with lymphadenopathy, pulmonary consolidation, and pleural effusion. Postprimary tuberculosis may manifest with cavities, consolidations, and centrilobular nodules. Miliary tuberculosis refers to hematogenously disseminated disease that is more commonly seen in immunocompromised patients, who present with miliary lung nodules and multiorgan involvement. The principal means of testing for active tuberculosis is sputum analysis, including smear, culture, and nucleic acid amplification testing. Imaging findings, particularly the presence of cavitation, can affect treatment decisions, such as the duration of therapy. Latent tuberculosis is an asymptomatic infection that can lead to postprimary tuberculosis in the future. Patients who are suspected of having latent tuberculosis may undergo targeted testing with a tuberculin skin test or interferon-γ release assay. Chest radiographs are used to stratify for risk and to assess for asymptomatic active disease. Sequelae of previous tuberculosis that is now inactive manifest characteristically as fibronodular opacities in the apical and upper lung zones. Stability of radiographic findings for 6 months distinguishes inactive from active disease. Nontuberculous mycobacterial disease can sometimes mimic the findings of active tuberculosis, and laboratory confirmation is required to make the distinction. Familiarity with the imaging, clinical, and laboratory features of tuberculosis is important for diagnosis and management. ^©RSNA, 2017.

Discontinuation of Respiratory Isolation for Possible Tuberculosis: Do Two Negative Sputum Smear Results Suffice?

Analysis of acid-fast bacillus smear results at a hospital with a mod-erate incidence of tuberculosis confirms recent recommendations that 2 negative smear results suffice for discontinuation of respiratory isolation. Use of polymerase chain reaction analysis further increases the confidence with which the diagnosis of active tuberculosis likely to be transmitted to others can be excluded.

Drug-resistant tuberculosis: controversies and challenges in pediatrics

Tuberculosis remains one of the top two causes of death caused by a single infectious disease worldwide, despite curative therapy. Children with tuberculosis are especially difficult to detect, since acid fast bacilli smears and cultures are usually negative and clinical signs are nonspecific or lacking. Multidrug-resistant tuberculosis, or tuberculosis resistant to at least isoniazid and rifampin, has emerged in most areas of the world over the past 20 years. Treatment of multidrug-resistant tuberculosis is more expensive and difficult. The second-line tuberculosis medications required for treatment are more toxic and less efficacious than standard treatment. These medications are not readily available in many areas of the world where drug resistance is most common. Fluoroquinolones are one of the most promising classes of second-line medications, but are not generally recommended for use in children. Ethambutol is recommended in the initial treatment of tuberculosis in children treated in areas where there is a risk of drug-resistant disease and the susceptibility of the source case is not known. Some experts have been hesitant to use ethambutol due to the risk of visual impairment associated with the drug and the difficulties in monitoring vision in young children. Pediatric drug formulations are not available for most antituberculosis medications, even the first-line tuberculosis drugs. Treatment of children exposed, infected or ill with multidrug-resistant tuberculosis is reviewed with special emphasis on second-line drugs, including recommended dosage, available formulations and necessary monitoring. While new cases of multidrug-resistant tuberculosis have decreased in most developed countries over the past 10 years, cases continue to increase in many developing countries and among immigrants from high-risk areas. Tuberculosis and multidrug-resistant tuberculosis are serious threats requiring worldwide strategies to control and treat. Better diagnostic tests, medications, public health strategies and vaccines will all be needed to eliminate tuberculosis.

Gastric Aspirate Yield For Children With Suspected Pulmonary Tuberculosis

The optimal number of gastric aspirates to diagnose tuberculosis is unclear. Thirty-two of 280 (11%) children in whom gastric aspirates were obtained grew Mycobacterium tuberculosis. First, second, and third specimens yielded initial culture positivity in 24 of 32, 6 of 32, and 2 of 24 cases, respectively. Intermittent positivity and paucibacillary disease necessitate obtaining multiple specimens.

Audit of the practice of sputum smear examination for patients with suspected pulmonary tuberculosis in Fiji

BACKGROUND

In Fiji, patients with suspected pulmonary tuberculosis (PTB) currently submit three sputum specimens for smear microscopy for acid-fast bacilli, but there is little information about how well this practice is carried out.

METHODS

A cross-sectional retrospective review was carried out in all four TB diagnostic laboratories in Fiji to determine among new patients presenting with suspected PTB in 2011: the quality of submitted sputum; the number of sputum samples submitted; the relationship between quality and number of submitted samples to smear-positivity; and positive yield from first, second and third samples.

RESULTS

Of 1940 patients with suspected PTB, 3522 sputum samples were submitted: 997 (51.4%) patients submitted one sample, 304 (15.7%) patients submitted two samples and 639 (32.9%) submitted three samples. Sputum quality was recorded in 2528 (71.8%) of samples, of which 1046 (41.4%) were of poor quality. Poor quality sputum was more frequent in females, inpatients and children (0-14 years). Good quality sputum and a higher number of submitted samples positively correlated with smear-positivity for acid-fast bacilli. There were 122 (6.3%) patients with suspected PTB who were sputum smear positive. Of those, 89 had submitted three sputum samples: 79 (89%) were diagnosed based on the first sputum sample, 6 (7%) on the second sample and 4 (4%) on the third sample.

CONCLUSION

This study shows that there are deficiencies in the practice of sputum smear examination in Fiji with respect to sputum quality and recommended number of submitted samples, although the results support the continued use of three sputum samples for TB diagnosis. Ways to improve sputum quality and adherence to recommended guidelines are needed.

Value of third sputum smear for detection of pulmonary tuberculosis in HIV infected patients

We evaluated diagnostic yield of third sputum smear in patients co infected with HIV for detection of pulmonary tuberculosis (TB). Among 139 pulmonary tuberculosis cases confirmed with positive sputum culture, diagnostic yield of first smear of sputum with acid fast staining was 81.9%. Incremental yield of 2^nd and 3^rd samples was 11.7% and 6.3% respectively. So two sputum smears may be enough for primary evaluation of HIV infected patients suspected to TB.

Cervical tuberculosis: a decision tree for protecting healthcare workers

OBJECTIVES/HYPOTHESIS

The clinical presentation of cervical tuberculosis (TB) is a unique challenge to the otolaryngologist. To minimize the risk of nosocomial transmission, otolaryngologists must suspect the diagnosis and be familiar with recommendations for TB prevention.

STUDY DESIGN

Scientific review.

METHODS

We review current literature and recent changes in TB prevention strategies including the Centers for Disease Control and Prevention "Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005."

RESULTS

Nosocomial transmission may occur from either unrecognized pulmonary disease or from aerosolization of tubercle bacilli during diagnostic procedures. History of prior TB infection, residence in a country where TB is endemic, close contact with a TB patient, or positive tuberculin skin test should raise suspicion of cervical TB. Physical examination findings may include painless, unilateral cervical lymphadenopathy. Children and human immunodeficiency virus infected patients present unique challenges, as these groups may have atypical presentations. When cervical TB is suspected, the provider should always screen for pulmonary and laryngeal disease. Fine needle aspiration with polymerase chain reaction or culture may accurately identify cervical TB. In rare cases, excisional biopsy may be required.

CONCLUSIONS

To facilitate interpretation and rapid diagnosis while minimizing risk to health care providers, we provide a decision tree based on new federal guidelines and the clinical experience of a team of infectious disease specialists and otolaryngologists.

Trends in tuberculosis/human immunodeficiency virus comorbidity, United States, 1993-2004

BACKGROUND

To our knowledge, this is the first assessment of trends in tuberculosis (TB)/human immunodeficiency virus (HIV) comorbidity in the United States based on national TB surveillance data.

METHODS

We analyzed all incident TB cases reported to the Centers for Disease Control and Prevention national TB surveillance system from all 50 states and the District of Columbia from 1993 through 2004. Trends in TB/HIV cases were examined according to selected demographic and clinical characteristics.

RESULTS

Cases of TB/HIV decreased from 3681 (15% of 25,108 TB cases) in 1993 to 1187 (8% of 14,515 TB cases) in 2004, accounting for 23% of the overall decrease in TB cases during this period. The TB/HIV case rate decreased from 1.4/100,000 in 1993 to 0.4/100,000 in 2004. The highest TB/HIV comorbidity rates persisted in persons aged 25 to 44 years (13.8%), males (9.7%), US-born persons (10.7%), non-Hispanic blacks (17.8%), and persons from the Northeast (11.0%) and the South (10.1%). Propensity stratification, used to account for the unequal probability of patients with TB being tested for HIV during the study period, did not show important differences in TB/HIV comorbidity trends.

CONCLUSIONS

Comorbidity due to TB/HIV decreased substantially between 1993 and 2004, primarily in US-born persons in states that experienced a TB resurgence between 1985 and 1992. These decreases coincide with improvements in TB control and advances in HIV treatment and diagnosis. The overall decreases obscure the wide variation in comorbidity that exists among some demographic groups and the recent slowing in the decline over the past 3 years.

Can the routine use of fluoroquinolones for community-acquired pneumonia delay the diagnosis of tuberculosis? A salutary case of diagnostic delay in a pilgrim returning from Mecca

Guidelines advocate using fluoroquinolones as first-line treatment for community-acquired pneumonia (CAP). However, the use of fluoroquinolones in patients with undiagnosed tuberculosis may cause a delay in the diagnosis of tuberculosis and may also promote the development of resistance to these drugs if used as monotherapy in undiagnosed tuberculosis. We illustrate the former with the following case report of a patient who developed tuberculosis after a pilgrimage to Mecca.