Analysis of tuberculosis prevalence surveys: new guidance on best-practice methods.

BACKGROUND: An unprecedented number of nationwide tuberculosis (TB) prevalence surveys will be implemented between 2010 and 2015, to better estimate the burden of disease caused by TB and assess whether global targets for TB control set for 2015 are achieved. It is crucial that results are analysed using best-practice methods. OBJECTIVE: To provide new theoretical and practical guidance on best-practice methods for the analysis of TB prevalence surveys, including analyses at the individual as well as cluster level and correction for biases arising from missing data. ANALYTIC METHODS: TB prevalence surveys have a cluster sample survey design; typically 50-100 clusters are selected, with 400-1000 eligible individuals in each cluster. The strategy recommended by the World Health Organization (WHO) for diagnosing pulmonary TB in a nationwide survey is symptom and chest X-ray screening, followed by smear microscopy and culture examinations for those with an abnormal X-ray and/or TB symptoms. Three possible methods of analysis are described and explained. Method 1 is restricted to participants, and individuals with missing data on smear and/or culture results are excluded. Method 2 includes all eligible individuals irrespective of participation, through multiple missing value imputation. Method 3 is restricted to participants, with multiple missing value imputation for individuals with missing smear and/or culture results, and inverse probability weighting to represent all eligible individuals. The results for each method are then compared and illustrated using data from the 2007 national TB prevalence survey in the Philippines. Simulation studies are used to investigate the performance of each method. KEY FINDINGS: A cluster-level analysis, and Methods 1 and 2, gave similar prevalence estimates (660 per 100,000 aged ≥ 10 years old), with a higher estimate using Method 3 (680 per 100,000). Simulation studies for each of 4 plausible scenarios show that Method 3 performs best, with Method 1 systematically underestimating TB prevalence by around 10%. CONCLUSION: Both cluster-level and individual-level analyses should be conducted, and individual-level analyses should be conducted both with and without multiple missing value imputation. Method 3 is the safest approach to correct the bias introduced by missing data and provides the single best estimate of TB prevalence at the population level.

Restarting the tuberculosis programme post-Haiyan.

PROBLEM: Typhoon Haiyan damaged or destroyed health infrastructure, equipment and services essential to the Philippine National Tuberculosis Programme (NTP), and it had to be re-established in the affected areas in Regions 6, 7 and 8. Continuing treatment and restoring diagnostic capacity were also challenging. CONTEXT: The Philippines has one of the highest tuberculosis (TB) burdens in the world. At the time of Typhoon Haiyan, there were an estimated 26 ,00 TB cases on treatment at directly observed treatment, short-course (DOTS) centres and 356 multidrug-resistant TB cases registered at programmatic management of drug-resistant TB (PMDT) sites. As TB was not included in the Philippines early-warning post-disaster surveillance system, tracking TB patients was difficult after Haiyan. ACTIONS AND OUTCOMES: Immediately following Haiyan, each aspect of the NTP was assessed to determine the extent of damage. TB patients were traced and services restored. We created maps showing the location of temporary TB diagnostic and treatment services, which hastened referrals. We provided new laboratory equipment, training and rapid testing capabilities in the affected regions. All TB services in the affected areas (473 DOTS, 490 TB microscopy and six PMDT facilities) were restored just two months after Haiyan. LESSONS LEARNT: Key lessons learnt from the NTP experience following Tyhoon Haiyan were: (1) the importance of having an electronic TB registry (database); (2) the need to include TB in the post-disaster surveillance system; (3) clear guidelines for TB control in disasters; and (4) the importance of coordination with all partners.

The tuberculosis profile of the Philippines, 2003-2011: advancing DOTS and beyond.

The Philippines is one of the highest tuberculosis (TB) burden countries in the world with nationwide coverage of directly observed treatment, short-course (DOTS) achieved in 2003. This study reports on the National TB Control Programme (NTP) surveillance data for the period 2003 to 2011. During this period, the number of TB symptomatics examined increased by 82% with 94% completing the required three diagnostic sputum microscopy examinations. Of the 1,379,390 cases diagnosed and given TB treatment, 98.9% were pulmonary TB cases. Of these, 54.9% were new smear-positive cases, 39.3% new smear-negative cases and 4.7% were cases previously treated. From 2008 to 2011, 50,030 TB cases were reported by non-NTP providers. Annual treatment success rates were over 85% with an average of 90%; the annual cure rates had an eight-year average of 82.1%. These surveillance data represent NTP priorities - the large proportion of smear-positive cases reflected the country's priority to treat highly infectious cases to cut the chain of transmission. The performance trend suggests that the Philippines is likely to achieve Millennium Development Goals and Stop TB targets before 2015.