New WHO policy and retooling activities for liquid culture systems
Microscopy examination of sputum specimens is still the most widely used in most developing countries for diagnosing tuberculosis (TB). Unfortunately, the relatively low sensitivity of sputum smear microscopy - even more so in the presence of HIV co-infection - is a major drawback to case-finding. The WHO Stop TB Strategy which underpins the Stop TB Partnership's Global Plan to Stop TB, 2006-2015 describes the principal approaches necessary to prevent and control TB, stressing the importance of case detection through quality-assured bacteriology (the Stop TB Strategy).
Rationale for liquid culture systems
Laboratory diagnosis of TB relies mostly on direct microscopic examination of sputum specimens in most TB prevalent countries. In addition to have low sensitivity, it cannot distinguish viable from nonviable organisms and cannot identify drug-resistant strains. Mycobacterial culture is more sensitive, but growth of TB bacilli on traditional solid medium requires up to eight weeks, which would delay appropriate treatment in the absence of a confirmed diagnosis. Laboratories also need to use a rapid and affordable method of species identification to differentiate between Mycobacterium tuberculosis complex and nontuberculous mycobacteria.
Expanding culture capacity and/or improving access to culture is urgently needed to address the diagnostic challenges due to the epidemics of HIV-associated TB and drug-resistant TB, especially in resource-limited settings. Liquid culture systems are the standard of care for TB diagnosis and patient management in industrialized countries. With increased sensitivity and reduced delays, liquid systems may contribute significantly to improve patient management.
Bio-safety conditions should be strictly followed to avoid risk of infection for laboratory staff. M. tuberculosis in aerosol is classified by WHO as a Risk Group organism, requiring biosafety level 3 laboratory safety precautions.
New WHO policy
WHO issued new policy recommendations on the use of liquid culture and rapid species identification in 2007. They recommend the use of both technologies within the context of country specific, comprehensive plans for laboratory capacity strengthening and based on a step-wise approach.
Preparing for country adoption, introduction, and implementation of liquid culture systems
Timely and effective adoption, introduction, and implementation of liquid culture systems by national TB programmes require significant stakeholder engagement, preparation, and communication.
At country level, the adoption of liquid culture systems is a multi-sector process leading to an explicit policy decision to access and use this technology. The policy decision follows an analysis of its benefits, risks, and costs and the health system’s capacity to finance, manage, and ensure its sustainable access and appropriate use. Ministries of Health should decide on the adoption of liquid culture systems in the context of a comprehensive and detailed country plan for strengthening laboratory capacity; moreover, they must communicate the policy decision before introducing and implementing the technology.
Introducing liquid culture and drug susceptibility testing (DST) systems requires countries to carry out coordinated activities to prepare for effective and sustainable access to this diagnostic technology. Such include ensuring appropriate regulation; preparing phase-in plans for equipment and supplies procurement and logistics management; revising guidelines, tools, and training materials; mobilizing financial resources; initiating staff training; country plans for expanding TB culture and DST should be based on a strong network of quality-assured microscopy, which remains the cornerstone for TB diagnosis. Laboratories should have demonstrated experience in cultures and DST using conventional methods. Countries should implement liquid systems,, starting with the national reference laboratory, and integrate them into a country-specific comprehensive plan for laboratory capacity strengthening that addresses the following key issues, at minimum:
- Appropriate biosafety level
- Detailed customer plan describing guarantees and commitments of the manufacturer
- Appropriate training of staff
- Maintenance of infrastructure and equipment in laboratories
- Quick transportation of samples from the peripheral to the culture laboratory
- Rapid communication of results
The implementation process encompasses the steps needed to operationalize the liquid culture and DST policy, including a system to monitor and evaluate the progress of these activities and their impact on tuberculosis control.
The Stop TB Partnership Task Force on Retooling has developed a checklist of key actions to facilitate global and country stakeholder planning for timely assessment, adoption, introduction, and implementation of the WHO recommendation, as appropriate. The guide illustrates actions that may be adapted to each country’s situation.
Engaging stakeholders from the wide range of constituencies affected by, and concerned with, TB-related issues will be essential. The retooling task force has developed a document to provide guidance to managers of national TB control programmes, other relevant public health programs and authorities, clinical laboratory and diagnostic services on identifying and engaging stakeholders. The document also provides simple tools for preparing a stakeholder engagement plan, and a list of suggested reading on the topic.
Finally, the Stop TB Partnership's Retooling Task Force has worked with WHO/Stop TB Department to include the retooling component in the WHO TB programme planning framework and in the costing and budgeting tool. It provides countries the opportunity to include a budget line for the implementation of liquid culture and DST.