Are peripheral microscopy centres ready for next generation molecular tuberculosis diagnostics?

Abstract

To the Editor: Sputum smear microscopy is the primary test for tuberculosis (TB) in most high-burden countries. Direct Ziehl–Neelsen (ZN) microscopy is routinely implemented in these countries via a vast network of decentralised, peripheral microscopy centres (as opposed to centralised reference laboratories), often located within primary or community health centres. This decentralised approach increases access in primary care settings and may help reduce diagnostic delays [1]. However, microscopy has limitations and novel diagnostics are urgently needed, particularly in settings with high prevalence of drug resistance and HIV [1, 2]. While Xpert® MTB/RIF (Cepheid, Sunnyvale, CA, USA), a World Health Organization-endorsed test, is already being rolled out in many countries, it is intended for district or sub-district laboratories [3], and not peripheral microscopy centres. In contrast, at least four next-generation nucleic-acid amplification tests (NAATs) are now on the market, with the goal of point-of-care (POC) use in peripheral laboratories [4, 5]. Can these so-called “POC-NAATs” actually be implemented in peripheral microscopy centres? Is there sufficient expertise ( e.g . to extract DNA) and biosafety ( e.g . to process sputum)? Will the necessary infrastructure ( e.g . stable power supply) be present? Will environmental conditions ( e.g . high temperature) limit their use? The introduction of novel diagnostics that aim to replace smear microscopy in peripheral laboratories is more likely to succeed if the new tests are designed with real world conditions in mind. However, there are limited data on landscape of microscopy centres in high-burden countries. We addressed this gap with a survey of 22 high-burden countries. We designed a one-page, 12-question survey. We focused on the most important requirements and considerations for the next generation of TB diagnostics. We included questions about ambient temperature and humidity conditions, safety, infrastructure, availability of equipment and …