Aid in Action
Infectious Diseases
TB, Malaria and Avian Influenza
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Monday, March 31, 2008
New Approaches:
1. Development of standard operating procedures (SOPs) for National TB Reference Laboratories (NRL)
WHO will liaise with a task force of international laboratory experts to develop a SOPs manual. In general, biosafety measures are often not clearly defined in all levels of TB laboratories. This subject has therefore been included in SOP guidelines to ensure adherence to good hygiene practices and safety procedures.
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2. Development of second-line drug susceptibility testing
In 1997 the World Health Organization (WHO), the International Union Against Tuberculosis and Lung Disease (IUATLD) and partners world-wide released the first report of the global project on anti-tuberculosis drug resistance.1 The data generated in this report were reinforced in a recently published second report.2 Directly observed treatment short-course (DOTS), the WHO strategy for TB control cures virtually all patients with drug-susceptible TB and some drugresistant TB through the administration of short-course chemotherapy with first-line drugs.3 However, patients with multidrug-resistant (MDR) tuberculosis (TB) to at least isoniazid and rifampicin are more likely to fail short-course chemotherapy. In recent years there has been encouraging evidence that patients with MDR TB can be cured with appropriate management based on second-line drugs.4-6 Unfortunately, second-line drugs are inherently more toxic and less effective than first-line drugs and reliable assessment of drug resistance is an essential prerequisite for appropriate use. Treatment is prolonged and significantly more expensive. Accurate laboratory drug susceptibility testing (DST) data to second-line drugs will support clinical decision making and help to prevent the emergence of further drug resistance in patients with MDR TB. In order to meet the challenges posed by MDR TB, the WHO established the DOTS-Plus.
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3. Development of training curricula on safety of NRL
The World Health Organization (WHO) has long recognized that safety and, in particular, biological safety are important international issues. WHO published the first edition of the Laboratory biosafety manual in 1983. The manual encouraged countries to accept and implement basic concepts in biological safety and to develop national codes of practice for the safe handling of pathogenic microorganisms in laboratories within their geographical borders. Since 1983, many countries have used the expert guidance provided in the manual to develop such codes of practice. A second edition of the manual was published in 1993.WHO continues to provide international leadership in biosafety through this third edition of the manual by addressing biological safety and security issues facing us in the current millennium. The third edition stresses throughout the importance of personal responsibility. New chapters have been added on risk assessment, safe use of recombinant DNA technology and transport of infectious materials.
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4. Functional quality assurance systems developed for TB labs
A number of key meetings and workshops were held where the TB case definition was discussed. These meetings included the Stop TB Partnership Laboratory Strengthening Subgroup (SLCS), an expert group meeting organized by the UNION held in Belgium and a technical expert workshop held in the Netherlands. Recent scientific evidence [Ref. 1,2] was reviewed and it was concluded that where a functional EQA for smear microscopy is in place, the finding of a single AFB in at least one single sputum smear examination in a TB suspect would satisfy the criterion to report a patient as having "sputum smear-positive tuberculosis" and to subsequently start treatment.
Given this policy revision, WHO will:
- guide and support countries in making country-specific plans of action for modifying all normative, training, and recording and reporting tools;
- provide technical assistance to countries to upgrade and fully expand functional external quality assurance (EQA) systems for TB laboratory services;
- provide guidance on study design, and sampling methodologies, in order to evaluate new diagnostic technologies (in collaboration with the Special Programme for Research and Training in Tropical Diseases (TDR));
- monitor and evaluate the impact of the change of policy on case detection at country level.
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5. Introduction of fluorescence microscopy in the sub-region
Fluorescence microscopy can be considered at all levels of the health system in high HIV prevalence countries seeking to improve the sensitivity of sputum microscopy, shorten time to diagnosis, and reduce laboratory workload. This technology has proven to be effective in high volume settings. Introduction of fluorescence microscopy in the sub-region.
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6. TB culture and drug susceptibility (DST) capacity in sub-region
Introduce or scale up facilities and technical capacity for mycobacterial culture services and drug susceptibility testing, and the incorporation of new diagnostic tools. While high quality sputum smear microscopy is the cornerstone of DOTS, and remains the key to case detection and TB control, the strengthening of services for culture of M. tuberculosis and for drug susceptibility testing (DST) is necessary, especially where the prevalence of HIV or MDR-TB is high. New diagnostic tools, expected to be introduced from 2008, will gradually replace sputum smear microscopy, conventional culture and DST. Countries will then require assistance with registration of new products, formulation of new policies, purchase of equipment, training and supervision of staff, and costs.
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7. MDR treatment referral centres strengthened: Because of the risk of severe morbidity and mortality to HIV-infected persons from MDRTB, persons with known MDRTB should receive routine care outside of normal HIV care settings. HIV care facilities can obtain estimates of the prevalence of MDRTB in their community from the local TB program. Through joint coordination and communication, the TB and HIV programs can plan for how to care for these patients. In areas where MDRTB is rare, special arrangements can be made to provide HIV care for an MDRTB patient. In areas where MDRTB is more prevalent, specialized clinics can be established.
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8. Strengthen the routine TB laboratory services
Why do we need to strengthen TB laboratories? The laboratory plays a critical role in identifying and diagnosing TB, caused by either drug-susceptible strains and drug-resistance strains. The laboratory also plays a role in monitoring treatment outcome and success. Few laboratories have the capacity to perform culture and drug susceptibility testing (DST) for first-line drugs and even fewer have the capacity to test for second-line drug resistance. WHO estimates that there are 400,000 cases of MDR-TB each year, but that less than 5% of these cases are currently detected.
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9. Strengthen the quality of the peripheral microscopy networks (TB)
As highlighted in the Stop TB Strategy, quality-assured bacteriological examination is an essential element for diagnosis and management of TB patients harbouring susceptible or resistant bacilli. During the last two years, an increasing number of countries are scaling up external quality assurance programmes for smear microscopy by means of blinded re-checking of slides. As a result, the quality of smear microscopy examination reached a satisfactory level in some countries. Evidence suggests that countries with a functional EQA system have very low frequency of false positive cases.
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10. Optimization of culture and drug susceptibility testing in the context of a TB control program , with emphais on more efficient diagnosis and drug resistance monitoring. The vision of the Stop TB Working Group on DOTS-Plus for MDR-TB is the integration of drug resistance surveillance and the management of MDR-TB as routine components of TB control, providing access to diagnosis and treatment for all TB patients and by all health care providers, regardless of drug susceptibility patterns. This is in line with the new WHO-recommended Stop TB strategy, which encompasses all TB patients, including those with MDR-TB and HIV. As a result, all MDR-TB management measures will be implemented in collaboration with DOTS expansion and strengthening activities, and in line with the activities of the other Partnership Working Groups.
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11. Management of MDR-TB in the sub-region Adapting DOTS to prevent and manage multidrug-resistant TB: DOTS-Plus. There are both preventive and restorative strategies to combat resistance to TB drugs – DOTS and DOTS-Plus – since DOTS alone is not sufficient to curb the TB epidemic in countries with high rates of multidrug-resistant TB and large proportions of re-treatment cases. The control of MDR-TB requires sound implementation of DOTS to prevent the development of new cases plus careful introduction of second-line drugs with adequate laboratory support to stop the amplification and circulation of resistant strains.
The priorities for the next decade are to:
- expand drug resistance surveillance (DRS);
- monitor trends and regularly update the global estimates of MDR-TB;
- strengthen capacity for quality-assured culture and drug susceptibility testing;
- dramatically scale up MDR-TB treatment according to WHO guidelines, since currently less than 2% of the total number of estimated culture-positive MDR-TB patients are treated appropriately;
- create a healthy and competitive market of quality-assured second-line drugs;
- provide technical and global coordination to accomplish the goals.
Strengthening of health systems and the health workforce to deliver sound diagnosis and treatment to all MDR-TB patients will be essential.
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12. Use of liquid culture and rapid species identification
Given current evidence and consensus, the Stop TB Partnership Laboratory Strengthening Subgroup, partner organizations, laboratory experts and the Strategic and Technical Advisory Group for tuberculosis recently endorsed the following WHO policies:
- The revision of the definition of a new sputum smear positive pulmonary TB case, based on the presence of at least one acid fast bacillus (AFB) in at least one sputum sample in countries with a well functioning external quality assurance system.
- The reduction of the number of specimens to be examined for screening of TB cases from three to two in places where workload is very high and human resources are limited. (If both smears are negative, then the algorithm for sputum negative cases applies.)
- The use of liquid culture and rapid species identification to address the needs for culture and drug susceptibility testing (DST), based on a country specific comprehensive plan for laboratory capacity strengthening. The use of liquid cultures and rapid species identification to be implemented as a step-wise approach.
Laboratory diagnosis of TB largely relies on the direct microscopic examination of sputum specimens. However, the technique, although specific, has low and variable sensitivity and cannot identify drug-resistant strains. Mycobacterial culture is more sensitive but growth of TB bacilli on traditional solid medium requires 4-8 weeks and consequently delays appropriate treatment in the absence of a confirmed diagnosis.
Expanding culture capacity is urgently needed to address challenges due to the epidemics of HIV-associated TB and drug resistant TB, especially in resource-limited settings.
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Training and Future Meetings:
Contact Person:
Connie Davis
Email: codavis@usaid.gov
Supported by USAID/EA, the NetMark Project increases African production of long-lasting insecticide treated nets for malaria prevention. Read more about NetMark at: http://www.netmarkafrica.org/