Prospective evaluation of a complex public health intervention: lessons from an initial and follow-up cross-sectional survey of the tuberculosis strain typing service in England

Abstract

BackgroundThe national tuberculosis strain typing service (TB-STS) was introduced in England in 2010. The TB-STS involves MIRU-VNTR typing of isolates from all TB patients for the prospective identification, reporting and investigation of TB strain typing clusters. As part of a mixed-method evaluation, we report on a repeated cross-sectional survey to illustrate the challenges surrounding the evaluation of a complex national public health intervention.MethodsAn online initial and follow-up questionnaire survey assessed the knowledge, attitudes and practices of public health staff, physicians and nurses working in TB control in November 2010 and March 2012. It included questions on the implementation, experience and uptake of the TB-STS. Participants that responded to both surveys were included in the analysis.Results248 participants responded to the initial survey and 137 of these responded to the follow-up survey (56% retention).Knowledge: A significant increase in knowledge was observed, including a rise in the proportion of respondents who had received training (28.6% to 67.9%, p = 0.003), and the self-rated knowledge of how to use strain typing had improved (‘no knowledge’ decreased from 43.2% to 27.4%).Attitudes: The majority of respondents found strain typing useful; the proportion that reported strain typing to be useful was similar across the two surveys (95.7% to 94.7%, p = 0.67).Practices: There were significant increases between the initial and follow-up surveys in the number of respondents who reported using strain typing (57.0% to 80.5%, p < 0.001) and the proportion of time health protection staff spent on investigating TB (2.74% to 7.08%, p = 0.04).ConclusionsEvaluation of a complex public health intervention is challenging. In this example, the immediate national roll-out of the TB-STS meant that a controlled survey design was not possible. This study informs the future development of the TB-STS by identifying the need for training to reach wider professional groups, and argues for its continuation based on service users’ perception that it is useful. By highlighting the importance of a well-defined sampling frame, collecting baseline information, and including all stakeholders, it provides lessons for the implementation of similar services in other countries and future evaluations of public health interventions.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2458-14-1023) contains supplementary material, which is available to authorized users.

The use of whole-genome sequencing in cluster investigation of a multidrug-resistant tuberculosis outbreak

“…Considerable time and resources were frequently invested without identifying additional epidemiological links, transmission settings, or cases. This may be due in part to MIRU-VNTR not being able to adequately distinguish clusters in some TB lineages or due to the high proportion of imported TB cases which reactivate in the UK [24]. Other low-incidence settings have found similar issues relating to the specificity of MIRU-VNTR [25].…”

The prospective evaluation of the TB strain typing service in England: a mixed methods study

“…We investigated the occurrence of false positive isolates, the contact tracing yield and diagnostic delay. These parameters, together with data obtained from initial and follow-up cross-sectional surveys evaluating user perception and implementation of the TB-STS, 8 were used to develop a mathematical model of effectiveness of the TB-STS, which informed a model of costeffectiveness (figure 1).…”

“…The arrows show how the different components of the evaluation were used to inform the semi-structured interviews and parameters for the transmission and cost-effectiveness models. Detailed results from the initial and follow-up surveys are presented elsewhere 8. TB-STS, TB strain typing service.…”

Data for action: collection and use of local data to end tuberculosis

“…Currently, such data are only collected broadly and systematically in resource-rich settings. For example, an analysis of United States national surveillance identified which racial minorities are most likely to develop TB from recent transmission, 51 and the United Kingdom has used molecular typing prospectively since 2010 to identify outbreaks 52 and to estimate the proportion and identity of MDR-TB cases attributable to transmission 53 . Locally, such data can also be used to improve both contact investigations (which may be complemented by online social network data 54 ) and the laboratory methods used to diagnose drug-resistant TB (Box 2).…”