MODS accreditation process for regional reference laboratories in Peru: validation by GenoType® MTBDRplus.

SETTING: Although considerable effort has been put into the development and evaluation of new diagnostics for tuberculosis (TB) and multidrug-resistant TB (MDR-TB), little attention has thus far been paid to the technical aspects of initiating quality-assured routine service use. For implementation of the microscopic-observation drug susceptibility (MODS) methodology in the Peruvian reference laboratory network, a laboratory accreditation process was devised; MODS results from an expert reference laboratory (Universidad Peruana Cayetano Heredia [UPCH]) were used as the standard against which implementing laboratory MODS results were judged to ensure that, prior to use for patient care, implementing laboratories achieved the same high performance with MODS as previously demonstrated in the research laboratory. OBJECTIVE: To evaluate the validity of MODS-based accreditation and the concordance of MODS drug susceptibility testing (DST) with molecular testing. DESIGN: Head-to-head comparison of MODS DST results from implementing Peruvian regional reference laboratories and the accrediting expert MODS laboratory (UPCH) with GenoType® MTBDRplus DST. RESULTS: The concordance of phenotypic MODS rifampicin (RMP) DST with GenoType MTBDRplus was respectively 97.4%, 97.9% and 97.1% for the two implementing regional laboratories and UPCH, and respectively 94.7%, 95.7% and 94.6% for isoniazid (INH) DST. CONCLUSION: High and consistent levels of MODS/MTBDRplus concordance for INH and RMP DST confirm the validity of the use of rapid methods as reference standards for accreditation.

Tuberculosis at the end of the 20th century in England and Wales: results of a national survey in 1998.

BACKGROUND: A national survey of tuberculosis was conducted in England and Wales in 1998 to obtain detailed information on the occurrence of the disease and recent trends. This survey also piloted the methodology for enhanced tuberculosis surveillance in England and Wales and investigated the prevalence of HIV infection in adults with tuberculosis. METHODS: Clinical and demographic data for all cases diagnosed during 1998 were obtained, together with microbiological data where available. Annual incidence rates in the population were estimated by age, sex, ethnic group, and geographical region using denominators from the 1998 Labour Force Survey. Incidence rates in different subgroups of the population were compared with the rates observed in previous surveys. The tuberculosis survey database for 1998 was matched against the Communicable Disease Surveillance Centre HIV/AIDS database to estimate the prevalence of HIV co-infection in adult patients with tuberculosis. RESULTS: A total of 5658 patients with tuberculosis were included in the survey in England and Wales (94% of all formally notified cases during the same period), giving an annual rate of 10.93 per 100 000 population (95% CI 10.87 to 10.99). This represented an increase of 11% in the number of cases since the survey in 1993 and 21% since 1988. In many regions case numbers have remained little changed since 1988, but in London an increase of 71% was observed. The number of children with tuberculosis has decreased by 10% since 1993. Annual rates of tuberculosis per 100 000 population have continued to decline among the white population (4.38) and those from the Indian subcontinent, although the rate for the latter has remained high at 121 per 100 000. Annual rates per 100 000 have increased in all other ethnic groups, especially among those of black African (210) and Chinese (77.3) origin. Over 50% of all patients were born outside the UK. Recent entrants to the UK had higher rates of the disease than those who had been in the country for more than 5 years or who had been born in the UK. An estimated 3.3% of all adults with tuberculosis were co-infected with HIV. CONCLUSIONS: The epidemiology of tuberculosis continues to change in England and Wales and the annual number of cases is rising. More than one third of cases now occur in young adults and rates are particularly high in those recently arrived from high prevalence areas of the world. The geographical distribution is uneven with urban centres having the highest rates. The increase in the number of cases in London is particularly large. Tuberculosis in patients co-infected with HIV makes a small but important contribution to the overall increase, particularly in London. To be most effective and to make the most efficient use of resources, tuberculosis prevention and control measures must be based on accurate and timely information on the occurrence of disease. A new system of continuous enhanced tuberculosis surveillance was introduced in 1999, based on the methodology developed in this national survey.

Molecular epidemiology of Mycobacterium avium complex isolated from patients with and without AIDS in Brazil and England.

Mycobacterium avium complex (MAC) is ubiquitous throughout the world. It is an opportunistic pathogen in AIDS patients but the number of cases in HIV negative patients is also increasing. The aim of this study was to determine whether patients were being infected with different MAC strains or whether one strain was dominant. DNA obtained from isolates in Brazil and England were compared using pulsed field gel electrophoresis (PFGE). Strains from 22 Brazilian patients clustered into 7 groups but 68/90 patients had a unique strain. In all patients, Brazilian and English, the same strain was isolated repeatedly over time, some over several years. This study shows that it is most likely that Man is infected from the environment and that one strain can survive without change for many years both in the environment and in Man.