Determination of critical concentrations of second-line anti-tuberculosis drugs with clinical and microbiological relevance

BACKGROUND

Reliable DST against second-line anti-tuberculosis drugs (SLDs) is crucial for the management of the increasing burden of patients affected by multidrug- and extensively drug-resistant TB.

METHODS

This study utilizes 252 clinical isolates of Mycobacterium tuberculosis from five countries (Hong Kong Special Administrative Region, Korea, Latvia, Peru, Philippines) with documented treatment histories to establish clinically and microbiologically relevant critical concentrations (CCs) of six SLDs for three routine testing methods: the absolute concentration method using Löwenstein-Jensen (LJ) medium, the 1% proportion method using Middlebrook 7H10 agar medium, and the radiometric BACTEC 460 system.

FINDINGS

In LJ medium, CCs of capreomycin, ethionamide, kanamycin, ofloxacin, rho-aminosalicylic acid and cycloserine (CS) were respectively 40.0, 40.0, 30.0, 3.0, 1.0 and 30.0 mg/l. In 7H10 agar medium, the respective CCs for the first five antibiotics (except CS) were 8.0, 2.0-3.0, 3.0-5.0, 1.0-1.5 and 0.5-1.0 mg/l. In BACTEC 460 broth, the respective CCs were 1.5-2.0, 1.0-1.5, 2.0-3.0, 0.5-1.0 and 0.5-1.0 mg/l. Precautions in DST interpretation was also discussed.

INTERPRETATION

By adopting this set of CCs as a global standard to define second-line drug susceptibility and resistance, as well as precautions in result interpretation, the screening, diagnosis and management of patients with drug-resistant TB can be greatly improved.

Targets for global tuberculosis control

The United Nations Millennium Development Goals (MDGs) have added to the suite of targets and indicators used to evaluate progress in tuberculosis (TB) control. This paper reviews the history of target setting for TB control and lays out the complete set of indicators and targets that will guide TB control through to 2015, the target year for all MDGs.

Speaking the same language: treatment outcome definitions for multidrug-resistant tuberculosis

SETTING

Globally it is estimated that 273000 new cases of multidrug-resistant tuberculosis (MDR-TB, resistance to isoniazid and rifampicin) occurred in 2000. To address MDR-TB management in the context of the DOTS strategy, the World Health Organization and partners have been promoting an expanded treatment strategy called DOTS-Plus. However, standard definitions for MDR-TB patient registration and treatment outcomes do not exist.

OBJECTIVE

To propose a standardized set of case registration groups and treatment outcome definitions for MDR-TB and procedures for conducting cohort analyses under the DOTS-Plus strategy.

DESIGN

Using published definitions for drug-susceptible TB as a guide, a 2-year-long series of meetings, conferences, and correspondence was undertaken to review published literature and country-specific program experience, and to develop international agreement.

RESULTS

Definitions were designed for MDR-TB patient categorization, smear and culture conversion, and treatment outcomes (cure, treatment completion, death, default, failure, transfer out). Standards for conducting outcome analyses were developed to ensure comparability between programs.

CONCLUSION

Optimal management strategies for MDR-TB have not been evaluated in controlled clinical trials. Standardized definitions and cohort analyses will facilitate assessment and comparison of program performance. These data will contribute to the evidence base to inform decision makers on approaches to MDR-TB control.

Frequency of recurrence among MDR-tB cases 'successfully' treated with standardised short-course chemotherapy

SETTING

Ivanovo Oblast, Russian Federation, 300 km north-east of Moscow, where a pilot DOTS TB control programme was implemented in October 1995.

OBJECTIVE

To determine the frequency of TB recurrence among MDR (multidrug-resistant) patients who achieved treatment 'success' on standard short-course chemotherapy.

METHODS

All patients with MDR tuberculosis, defined as resistance to at least isoniazid and rifampicin, who were declared 'cured' or 'treatment completed', were identified using the district register and traced whenever possible. Eligible patients underwent medical examination and, if necessary, chest radiography, sputum smear examination, culture and susceptibility testing. If the patient had died, the relatives were interviewed to try to determine the reasons for death.

RESULTS

Of 18 patients eligible for analysis, five (27.8%) were documented to have recurrence (two of seven patients resistant to HRSE, one of five patients resistant to HRS and two of six patients resistant to HR). Patients receiving the Category I regimen were more likely to relapse than those receiving the Category II regimen (40% vs. 12.5%). The median time to relapse was 8 months; 2.46 recurrences were observed in 100 person-months (3.17 in category I and 1.3 in Category II patients).

CONCLUSIONS

The frequency of TB recurrence among MDR-TB patients declared 'cured' after short-course chemotherapy is high. Improvements in treatment success, after removal of programme-related pitfalls in the treatment delivery process, must incorporate methods for early detection of MDR, along with adequate treatment regimens including second-line drugs. Culture-based bacteriological confirmation at the end of treatment is recommended.

Quality assurance programme for drug susceptibility testing of Mycobacterium tuberculosis in the WHO/IUATLD Supranational Reference Laboratory Network: five rounds of proficiency testing, 1994-1998

SETTING

Quality assurance for the WHO/IUATLD Global Tuberculosis Drug Resistance Surveillance Programme.

OBJECTIVE

To implement an ongoing proficiency-testing programme for drug susceptibility testing (DST) of Mycobacterium tuberculosis within the WHO/IUATLD Supranational Reference Laboratories Network (SRLN).

DESIGN

Five culture panels, each consisting of 10 duplicate drug-susceptible and drug-resistant clinical isolates (100 strains) of M. tuberculosis were tested for resistance to streptomycin (SM), isoniazid (INH), rifampicin (RMP) and ethambutol (EMB). DST procedures included the proportion, absolute concentration and resistance ratio methods, as well as the radiometric BACTEC 460 method.

RESULTS

The efficiency, sensitivity and specificity of M. tuberculosis DST as well as the intra-laboratory reproducibility showed that the laboratories tested susceptibility to RMP and to INH very reliably, with values ranging from 97% to 99%. The testing of SM and EMB was less dependable, with values ranging from 90% to 95%. The sensitivity of testing of EMB increased from 60% in Round 1 to 98% in Round 5, without a concomitant decrease in specificity.

CONCLUSIONS

This study has shown that regular proficiency testing can significantly improve the quality of DST, even in the most sophisticated TB laboratories. Mean DST efficiency levels of 92% for both SM and EMB and 97% and 99% for INH and RMP, respectively, are proposed as reasonable performance goals for the SRL network. Efficiency, consistently lower than these values, would require remedial action. Efficiency levels lower than mean -1 standard error, i.e., 80% for SM and EMB, 89% for INH and 95% for RMP, should always be considered as sub-standard performance for DST.

Sensitivity and specificity of transesophageal echocardiography for determination of aortic valve morphology

BACKGROUND

Preoperative recognition of the presence of bicuspid aortic valve can be important in the planning of procedures. Multiplane transesophageal echocardiography may allow more accurate detection of valvular morphology than does biplane transesophageal echocardiography.

METHODS AND RESULTS

The studies of 710 patients who subsequently underwent valvular or aortic surgery were reviewed in a blinded fashion. The inclusion criteria were adequate short-axis view and operative note confirmation of aortic valve morphology. Six hundred eight patients were submitted to further analysis. Four hundred three patients had aortic stenosis as the primary diagnosis. Three hundred sixty patients had biplane examinations and 248 had multiplane examinations. The sensitivity and specificity of the multiplane technique in assessing aortic valve morphology (bicuspid vs tricuspid valve) was 87% and 91%, respectively. The sensitivity and specificity of the biplane technique was 66% and 56%, respectively. Whether valves were calcified or not did not result in major changes in sensitivity and specificity for either technique.

CONCLUSIONS

Multiplane transesophageal echocardiography provides a more accurate assessment of preoperative aortic valve morphology than does the biplane approach in the majority of patients.

Comparison of multiplane and biplane transesophageal echocardiography in the assessment of aortic stenosis

The aim of the study was to compare the accuracy of multiplane transesophageal echocardiography (TEE) with the more conventional biplane technique in the direct assessment of aortic valve area in patients with aortic stenosis. Short-axis images of the aortic valve adequate for measuring aortic valve area were obtained in all 81 patients studied by multiplane TEE but in only 56 of 64 patients (88%) using the biplane approach. The correlation coefficient for aortic valve area determined by multiplane TEE (r = 0.89; SEE = 0.04 cm2) was higher (p < 0.01) than biplane TEE (r = 0.74; SEE = 0.06 cm2). Correlations were higher for bicuspid valves (multiplane, r = 0.93; biplane, r = 0.75) than tricuspid valves (multiplane, r = 0.87; biplane, r = 0.75). Our study has demonstrated the superiority of multiplane TEE to both biplane TEE and transthoracic echocardiography (TTE) in the direct evaluation of aortic valve area in patients with aortic stenosis.

[Hepatic markers (Ac-HVA-IgM and AcHBc-IgM) in cases of infectious hepatitis in Dominican children]

The presence of IgM antibodies for the HVA and HBc antigens in 90 children of 15 or less years with acute hepatitis were investigated, finding that 62% (58) were positive for HVA, 8.9% (8) for HBc and 27.8% (25) did not show antibodies for HVA or HBc (non-A non-B hepatitis); comments are made on some clinical and epidemiological findings such as a higher frequency of blood transfusions in HNANB, more males in HB and HNANB, and more hepatomegaly and liver sensitivity in HNANB.