ECG monitoring in STREAM Stage 1: can we identify those at increased risk of QT prolongation?

BACKGROUND: STREAM (Standardised Treatment Regimen of Anti-tuberculosis Drugs for Patients with Multidrug-resistant Tuberculosis) Stage 1 was a randomised trial of a Short (9-month) regimen for rifampicin-resistant TB (RR-TB). QT or QTcF prolongation ≥500 ms occurred in 31 (11%) of 282 Short regimen participants. The frequent ECG monitoring employed might be challenging for treatment programmes. This analysis aimed to determine whether those at higher risk of severe QT prolongation could be identified early for more targeted monitoring.METHODS: Data from the first month of treatment were used to investigate whether participants were at risk of developing QT/QTcF ≥500 ms. QTcF increases from baseline at different time points were examined. Absolute QTcF measurements were categorised in 5 ms increments at each time-point. The most discriminating time points and QTcF cut-offs were combined to optimise sensitivity and specificity.RESULTS: Absolute QTcF values were more discriminating than magnitude of increase from baseline. More participants who developed QT/QTcF ≥500 ms had a QTcF of respectively ≥425 ms and ≥430 ms at 4 h and Week 3 (P < 0.05) than those who did not. By combining QTcF values ≥425 ms at 4 h and ≥430 ms at Week 3, we identified high-risk participants with 97% sensitivity and 99% negative predictive value.CONCLUSION: Reduced ECG monitoring may be possible for many Short regimen participants.

Failure or relapse predictors for the STREAM Stage 1 short regimen for RR-TB

BACKGROUND: STREAM (Standardised Treatment Regimens of Anti-tuberculosis drugs for Multidrug-Resistant Tuberculosis) Stage 1 demonstrated non-inferior efficacy of a short regimen for rifampicin-resistant TB (RR-TB) compared to a long regimen as recommended by the WHO. The present paper analyses factors associated with a definite or probable failure or relapse (FoR) event in participants receiving the Short regimen.METHODS: This analysis is restricted to 253 participants allocated to the Short regimen and is based on the protocol-defined modified intention to treat (mITT) population. Multivariable Cox regression models were built using backwards elimination with an exit probability of P = 0.157, equivalent to the Akaike Information Criterion, to identify factors independently associated with a definite or probable FoR event.RESULTS: Four baseline factors were identified as being significantly associated with the risk of definite or probable FoR (male sex, a heavily positive baseline smear grade, HIV co-infection and the presence of costophrenic obliteration). There was evidence of association of culture positivity at Week 8 and FoR in a second model and Week 16 smear positivity, presence of diabetes and of smoking in a third model.CONCLUSION: The factors associated with FoR outcomes identified in this analysis should be considered when determining the optimal shortened treatment regimen.

QT prolongation in the STREAM Stage 1 Trial

BACKGROUND: STREAM (Standardized Treatment Regimen of Anti-TB Drugs for Patients with MDR-TB) Stage 1 demonstrated non-inferior efficacy of a shortened regimen (the Short regimen) for rifampicin-resistant TB (RR-TB) compared to the contemporaneous WHO-recommended regimen. This regimen included moxifloxacin and clofazimine, known to cause QT prolongation, and severe prolongation was more common on the Short regimen. Here we investigate risk factors for QT prolongation with the Short regimen.METHODS: Data from patients prescribed the Short regimen (n = 282) were analysed to identify risk factors for severe QT prolongation (QT/QTcF ≥500 ms or ≥60 ms increase in QTcF from baseline).RESULTS: Of the 282 patients on the Short regimen, 94 (33.3%) developed severe QT prolongation: 31 QT/QTcF ≥500 ms; 92 experienced ≥60 ms QTcF increase from baseline. The median time to QT/QTcF ≥500 ms was 20 weeks (IQR 8-28), and the time to ≥60 ms increase from baseline was 18 weeks (IQR 8-28). Prolongation ≥500 ms was most frequent in patients from Mongolia (10/22, 45.5%) compared with 3.5-11.9% at other sites, P < 0.001. Higher baseline QTcF increased risk of prolongation to ≥500 ms (QTcF ≥400 ms: OR 5.99, 95% CI 2.04-17.62).CONCLUSION: One third of patients on the Short regimen developed severe QT prolongation. QT/QTcF ≥500 ms was more common in patients from Mongolia and in those with a higher baseline QTcF, which may have implications for implementation of treatment.

Investigation of the efficacy of the short regimen for rifampicin-resistant TB from the STREAM trial

BACKGROUND

The STREAM trial demonstrated that a 9-11-month "short" regimen had non-inferior efficacy and comparable safety to a 20+ month "long" regimen for the treatment of rifampicin-resistant tuberculosis. Imbalance in the components of the composite primary outcome merited further investigation.

METHODS

Firstly, the STREAM primary outcomes were mapped to alternatives in current use, including WHO programmatic outcome definitions and other recently proposed modifications for programmatic or research purposes. Secondly, the outcomes were re-classified according to the likelihood that it was a Failure or Relapse (FoR) event on a 5-point Likert scale: Definite, Probable, Possible, Unlikely, and Highly Unlikely. Sensitivity analyses were employed to explore the impact of informative censoring. The protocol-defined modified intention-to-treat (MITT) analysis population was used for all analyses.

RESULTS

Cure on the short regimen ranged from 75.1 to 84.2% across five alternative outcomes. However, between-regimens results did not exceed 1.3% in favor of the long regimen (95% CI upper bound 10.1%), similar to the primary efficacy results from the trial. Considering only Definite or Probable FoR events, there was weak evidence of a higher risk of FoR in the short regimen, HR 2.19 (95%CI 0.90, 5.35), p = 0.076; considering only Definite FoR events, the evidence was stronger, HR 3.53 (95%CI 1.05, 11.87), p = 0.030. Cumulative number of grade 3-4 AEs was the strongest predictor of censoring. Considering a larger effect of informative censoring attenuated treatment differences, although 95% CI were very wide.

CONCLUSION

Five alternative outcome definitions gave similar overall results. The risk of failure or relapse (FoR) may be higher in the short regimen than in the long regimen, highlighting the importance of how loss to follow-up and other censoring is accounted for in analyses. The outcome of time to FoR should be considered as a primary outcome for future drug-sensitive and drug-resistant TB treatment trials, provided sensitivity analyses exploring the impact of departures from independent censoring are also included.

Gender differences in tuberculosis treatment outcomes: a post hoc analysis of the REMoxTB study

BACKGROUND

In the REMoxTB study of 4-month treatment-shortening regimens containing moxifloxacin compared to the standard 6-month regimen for tuberculosis, the proportion of unfavourable outcomes for women was similar in all study arms, but men had more frequent unfavourable outcomes (bacteriologically or clinically defined failure or relapse within 18 months after randomisation) on the shortened moxifloxacin-containing regimens. The reason for this gender disparity in treatment outcome is poorly understood.

METHODS

The gender differences in baseline variables were calculated, as was time to smear and culture conversion and Kaplan-Meier plots were constructed. In post hoc exploratory analyses, multivariable logistic regression modelling and an observed case analysis were used to explore factors associated with both gender and unfavourable treatment outcome.

RESULTS

The per-protocol population included 472/1548 (30%) women. Women were younger and had lower rates of cavitation, smoking and weight (all p < 0.05) and higher prevalence of HIV (10% vs 6%, p = 0.001). They received higher doses (mg/kg) than men of rifampicin, isoniazid, pyrazinamide and moxifloxacin (p ≤ 0.005). There was no difference in baseline smear grading or mycobacterial growth indicator tube (MGIT) time to positivity. Women converted to negative cultures more quickly than men on Lowenstein-Jensen (HR 1.14, p = 0.008) and MGIT media (HR 1.19, p < 0.001). In men, the presence of cavitation, positive HIV status, higher age, lower BMI and 'ever smoked' were independently associated with unfavourable treatment outcome. In women, only 'ever smoked' was independently associated with unfavourable treatment outcome. Only for cavitation was there a gender difference in treatment outcomes by regimen; their outcome in the 4-month arms was significantly poorer compared to the 6-month treatment arm (p < 0.001). Women, with or without cavities, and men without cavities had a similar outcome on all treatment arms (p = 0.218, 0.224 and 0.689 respectively). For all other covariate subgroups, there were no differences in treatment effects for men or women.

CONCLUSIONS

Gender differences in TB treatment responses for the shorter regimens in the REMoxTB study may be explained by poor outcomes in men with cavitation on the moxifloxacin-containing regimens. We observed that women with cavities, or without, on the 4-month moxifloxacin regimens had similar outcomes to all patients on the standard 6-month treatment. The biological reasons for this difference are poorly understood and require further exploration.

Isocyanate exposure and occupational asthma: a case-referent study

OBJECTIVE

To examine the quantitative relation between exposure to isocyanates and occupational asthma, and to explore the role of atopy and smoking in occurrence of the disease.

METHOD

A case-referent study was undertaken of cases from two manufacturing companies (A and B) from which referents without disease could be selected and reliable exposure measurements were available. In company A, 27 cases mainly attributed to toluene diisocyanate (TDI) were matched to 51 referents on work area, start and duration of employment, sex, and age. Exposures were estimated from existing measurements by job category. In company B there were seven cases attributed to 4,4'-diphenylmethane diisocyanate (MDI) in two areas of the plant; 12 non-cases from the same areas were used as referents. Personal exposure measurements were available for all cases and 11 referents.

RESULTS

No difference in peak exposures between cases and referents was found in either plant; but in both, time weighted average (TWA) exposures at the time of onset of asthma were higher for cases. In A, the mean TWA exposure for cases was 1.5 (95% confidence interval (95% CI) 1.2 to 1.8) ppb compared with 1.2 (1.0 to 1.4) ppb for referents. From a matched analysis, the odds ratio (OR) associated with 8 hour TWA exposure to isocyanates greater than 1.125 ppb (the median concentration for the referent group) was 3.2 (95% CI 0.96 to 10.6; p=0.06). Occupational asthma was associated with a pre-employment history of atopic illness (OR 3. 5, p=0.04) and, less strongly, with smoking (OR 2.1, p=0.14). In B, small numbers limited analysis, but three of seven cases had at least one TWA exposure measurement greater than 5 ppb compared with one of 11 referents (OR 7.5, p=0.09).

CONCLUSION

Asthma can occur at low concentrations of isocyanates, but even at low concentrations, the higher the exposure the greater the risk. By contrast with other studies, smoking and atopy seemed to increase the odds of occupational asthma due to isocyanates, but did not affect the estimate of risk associated with exposure.

Reported incidence of occupational asthma in the United Kingdom, 1989-97

OBJECTIVES

To examine trends in estimated population based incidence of occupational asthma by age, sex, occupation, geographical region, and causal agents based on 9 years of the Surveillance of Work Related and Occupational Respiratory Disease (SWORD) data.

METHODS

In January 1989 the SWORD scheme for the surveillance of occupational respiratory disease was established in the United Kingdom to make good the lack of epidemiological information on the incidence of these diseases in the United Kingdom. Between 80% and 90% of chest and occupational physicians report voluntarily all new cases they see, on a monthly or random sampling basis. During the 9 years 1989-97, an estimated 25 674 new cases of occupational respiratory disease, including 7387 of occupational asthma, were reported. Suspected causal agents were classified into 44 categories and estimated annual incidences of asthma were calculated with denominators from the labour force survey.

RESULTS

Overall, a third of the suspected causes of asthma were organic, a third chemical, 6% metallic, and the rest miscellaneous, or in 8%, unknown. There was evidence of an increase since 1989 in cases due to latex, and possibly glutaraldehyde, and an apparent drop since 1991 in the proportion of cases attributed to isocyanates. Incidences were higher in men than women and the disparity was especially marked in the population aged 45 years or more in which rates for men were at least twice those for women. Average annual rates per million workers for 1992-7 ranged from 7 (95% confidence interval (95% CI) 5 to 9) for the lowest risk group of professional, clerical, and service workers to 1464 (95% CI 968 to 2173) for coach and other spray painters. Except for laboratory technicians, all other occupations with rates over 100 were concerned with manufacturing and processing that used chemicals, metals, and organic materials. Incidences were two to three times higher in the north and midlands than in East Anglia and the south. The introduction of a sampling scheme in 1992 doubled estimates of reported incidence of occupational asthma, but there was little evidence of other temporal changes.

CONCLUSIONS

The SWORD scheme has produced consistent estimates of the causes and incidence of occupational asthma as seen by chest and occupational physicians. It has allowed the epidemiology of occupational asthma in the population to be studied and high risk occupations to be identified. There is certainly more occupational asthma in the population than that which reaches specialists in occupational and chest medicine; therefore the incidence rates presented here are underestimates, but by how much remains unknown.

SWORD '93. Surveillance of work-related and occupational respiratory disease in the UK

Some 3500 new cases of occupational respiratory disease are estimated to have been seen annually by SWORD participants in 1992 and 1993 with little important difference between the two years. As the number of new cases recognized and reported by chest physicians is close to complete, the estimated incidence is essentially correct. The pattern of disease which clearly emerges shows that at least half is attributable to asbestos exposure, despite the fact that lung cancer from this cause may be under-reported. Benign pleural disease comprises a large proportion of the cases, the long-term implications of which are unknown. Almost 40% of the cases reported are of occupational asthma or inhalation accidents, both due to a very large number of different agents and affecting many and varied occupations. These cases are preventable providing their occupational aetiology is recognized and appropriate measures of control are intensified.

Work-related respiratory disease in the United Kingdom, 1989-1992: report on the SWORD project

The objective of this project is the creation of a reliable and cost-effective national system of surveillance for work-related respiratory disease as a basis for control and simple epidemiological research. With the voluntary participation of almost 800 chest and occupational physicians from throughout the UK, newly diagnosed cases of respiratory illness thought to be due to occupational factors have been reported regularly since January 1989. Since January 1992, reports from chest physicians have been submitted monthly by a core group with special interest in occupational lung disease (n = 32) and rotating random samples of the remainder. Between 1989 and 1991, 5576 new cases were reported, of which half were diseases of long latency mainly due to asbestos, 28% were occupational asthma, and the rest were divided between inhalation accidents (10%) and a variety of other acute diseases (14%). Disease incidence rates, with denominators from the Labour Force Survey, showed a very high risk of asthma among paint sprayers, chemical and food processors, laboratory staff, plastics and metal treatment workers, and in welding and electronic assembly. Some of the same groups also experienced high rates of inhalation accidents and bronchitis. The risk of diseases of long latency, using denominators from the 1961 census, was highest in shipyard and dock workers, miners and construction workers. The SWORD scheme has provided estimates of disease incidence not previously available, has encouraged awareness of occupational factors among chest physicians, has assisted those responsible for prevention and control, and has demonstrated the feasibility of this approach to surveillance.

Tuberculosis and HIV: estimates of the overlap in England and Wales

BACKGROUND

A study was designed to determine the extent of the interaction between tuberculosis and human immunodeficiency virus infection in England and Wales.

METHODS

Data were obtained from the United Kingdom national AIDS surveillance and the Medical Research Council tuberculosis notification surveys in England and Wales (1983 and 1988). The proportion of patients reported with AIDS known to have had tuberculosis and the proportion of patients notified with tuberculosis known to have HIV infection were estimated.

RESULTS

Of the 4360 patients with AIDS reported by 30 June 1991, 200 (4.6%) were in patients reported to have had tuberculosis. Only one of the 3002 patients (0.03%) reported in the 1983 survey of tuberculosis notifications in England and Wales was known to be infected with HIV compared with nine of 2163 patients (0.42%) in the 1988 survey.

CONCLUSION

Although the reported number of cases of HIV infection with tuberculosis in this country is increasing it remains small. Complete reporting of cases of AIDS and notification of cases of tuberculosis are essential to enable the two infections to be monitored as the HIV epidemic develops. Special studies, such as those reported here, will need to be undertaken regularly to assess the future extent of the interaction.

Occupational respiratory disease in the United Kingdom 1989: a report to the British Thoracic Society and the Society of Occupational Medicine by the SWORD project group

A voluntary scheme for the surveillance of work related and occupational respiratory disease (SWORD) was established in January 1989 with help from the British Thoracic Society and the Society of Occupational Medicine and support from the Health and Safety Executive. Three hundred and fifty four chest physicians representing 90% of the chest clinics in the United Kingdom and 361 occupational physicians submit reports regularly of newly diagnosed cases of work related respiratory illness with information on age, sex, residence, occupation, and suspected causal agent. In 1989 2101 cases were notified, of which frequent diagnoses were asthma (26%), mesothelioma (16%), pneumoconiosis (15%), benign pleural disease (11%), and allergic alveolitis (6%). Incidence rates calculated against denominators from the Labour Force Survey showed very large differences between occupational groups, especially for asthma and asbestos related diseases. Substantial regional variation in the incidence of asthma was not explained by the geographical distribution of high risk industries and was probably due to differing levels of ascertainment. The results imply that the true frequency of acute occupational respiratory disease in the United Kingdom may have been three times greater than that reported.

Deaths in adults with notified pulmonary tuberculosis 1983-5

For a study of fatality in pulmonary tuberculosis in England and Wales, a sample (n = 1222) of patients notified in 1983 as having tuberculosis confined to the lungs was selected and their mortality up to the time of finishing chemotherapy calculated. During that time 158 patients died, a case fatality of 12.9%. Stratification by age and radiographic extent of disease confirmed these as important predictors of death. Comparison with a referent population showed that the all cause mortality among people with pulmonary tuberculosis was 10 times greater than that of the age and sex matched general population. This ratio fell with increasing age and with extent of disease. Coefficients derived from a logistic regression analysis allowed probability of death during chemotherapy of patients with pulmonary tuberculosis to be estimated.