Policy guidance on TB drug susceptibility testing (DST) of second-line drugs (SLD)
Geneva, 23 July 2007 - The world's leading TB laboratory specialists have issued initial policy recommendations to guide national TB programmes embarking on second-line drug susceptibility testing.
The three main objectives of a meeting, hosted by the WHO Stop TB Department, were to develop an interim policy document; update existing technical guidelines; and develop plans for external quality assurance of second-line drug susceptibility testing.
The Expert Group issued the following statement:
There are an estimated 424,000 multidrug-resistant TB (MDR-TB) cases each year and approximately 25,000 of these cases are expected to have extensively drug-resistant TB (XDR-TB). The Global Plan to Stop TB outlines scale up of services within TB programmes to detect and treat 1.6 million MDR-TB cases by 2015. The laboratory plays a critical role in identifying MDR and XDR-TB cases; however, as a result of historical neglect, few national TB programmes have capacity for drug-susceptibility testing (DST) for the first-line drugs and even fewer have the capacity to test for second-line drug resistance. Assessment of recent laboratory capacity indicates that less than 5% of MDR-TB cases are currently detected.
In order to achieve the ambitious new goals to treat MDR-TB, laboratories must develop the capacity to diagnose and follow up these cases using algorithms including first- and second-line DST and use of rapid methods.
Guidance on susceptibility testing for second-line drugs was published in 2001 by WHO. Since that time new testing methods have been developed and additional standardization of existing methodologies has been undertaken.
In response to the need for updated guidance, the WHO Stop TB Department held a two day expert group meeting to develop a framework for policy guidance to national TB programmes embarking on MDR-TB treatment programmes. The three main objectives of the meeting were develop an interim policy document, update existing technical guidelines, and develop plans for external quality assurance of second-line DST.
The expert group reviewed current evidence and re-confirmed that the laboratory diagnosis of MDR and XDR-TB under good laboratory practice is reliable and reproducible. In addition this consultative process culminated in an interim policy guidance document which summarizes available evidence on the second-line DST methods, provides recommendations for which drugs to test as well as the critical concentrations. The document also provides programmatic advice on designing diagnostic algorithms, required lab capacity and safety requirements. The policy document will be available on the WHO web site by the end of August this year.
The expert group also developed a detailed outline for the update of the 2001 technical guidelines for drug-susceptibility testing of second line drugs, incorporating the newer technologies. A writing committee was established with the aim of releasing the updated guidelines by the end of this year.
Quality assurance of laboratory testing is critical in ensuring that diagnosis is accurate. External quality assurance for DST of first-line drugs was begun internationally in 1993 through the Supranational Laboratory Network. The network of 26 laboratories now provides proficiency testing panels to over 120 laboratories worldwide. In this regard, the expert group reviewed available data from a sub-network that has been establishing a proficiency testing panel for second-line DST. From this year forward, SLDs will be included in the annual SRLN proficiency testing programme.
The expert group strongly called on governments and donor agencies to significantly increase financial and human resource investment in laboratory services in order to appropriately respond to the increased threat of MDR and XDR-TB. As outlined in the recently published Stop TB Partnership and WHO Response Plan for MDR-TB and XDR-TB, an investment of $168m for lab services will be required in the next two years.
Expert Group Meeting,
WHO, Geneva, Switzerland
16-17 July 2007