TB Laboratory Network

Prompt diagnosis of both drug-susceptible and drug-resistant TB cases is the first step to achieve TB control. A strong and efficient laboratory network, providing diagnosis according to the established diagnostic algorithm and under quality assured procedures is the key component for this task. The role of laboratories at different levels includes services for the management of individual patients (diagnosis of TB and DR-TB, treatment follow up, DST for regimen) and programmatic activities (TB prevalence surveillance, monitoring trends of drug resistance). The laboratory network is coordinated at the central level by the laboratory team of the NTBLCP. 

The laboratory network is divided into four levels, with a pyramidal setup: two national reference laboratories (NRLs), six Zonal Reference Laboratories (ZRLs), a state level laboratory in each state and peripheral facilities (see Figure 4). This classification is based on administrative division, geographic location, population coverage and type of activities implemented at various levels. 

 

At the top of the pyramidal structure are the two NRLs, located at the National TB and Leprosy Training Centre (NTBLTC), Zaria and the Nigerian Institute of Medical Research (NIMR) in Lagos, in the northern and southern parts of the country, respectively. The Zaria NRL is structurally located within the NTBLCP and as such reports directly to the NTBLCP central unit. NIMR, however, is a parastatal within the Federal Ministry of Health that does not report directly to the NTBLCP. 

The activities implemented at the NRLs include microscopy (LED and/or light), culture (solid and liquid), identification of MTB complex by immunochromatographic methods and the most common species of non-tuberculous Mycobacteria (NTMs) by LPA; molecular methods for detection of drug resistance (LPA and GeneXpert); and DST according to the WHO guidelines for first-line anti-TB drugs (FLDs) and second-line anti-TB drugs (SLDs). FLDs tested include isoniazid, rifampicin and ethambutol (streptomycin was discontinued early 2014). SLDs tested include capreomycin, kanamycin, amikacin, aminoglycosides, levofloxacin, ofloxacin, ethionamide and cycloserine, with plans to add moxifloxacin and pyrazinamide). Trainings, panel testing, supervision of ZRLs, preparation of media and research activities are also regularly performed. The NRLs are affiliated with the supranational reference laboratory (SRL) in Milan, Italy. The SRL provides support in programmatic and technical aspects related to laboratory network implementation, in particular to support DR-TB diagnostics activities and EQA. Both the NRLs have successfully performed the EQA and DST for first-line drugs (2012-2013) and one of them is under validation for second-line DST by the SRL as of June 2014. 

As at early, 2014, the NRLs have commenced accreditation process according to the WHO African Region Stepwise Laboratory Improvement Process Towards Accreditation. Other NSP-TB 2015 – 2020: Towards Universal Access to Prevention, Diagnosis and Treatment Page 33 

laboratories, University College Hospital (UCH) Ibadan, Dr. Lawrence Henshaw Hospital (DLHMH), Calabar and Zankli Medical Centre (a privately owned laboratory in Abuja) are at different stages of accreditation, but they all plan to achieve accreditation within the period of this NSP. 

The next level is the ZRLs, strategically located in the six geo-political zones of Nigeria. These laboratories are sited within university teaching hospitals and are meant to carry out the following activities: culture (solid and nitrate reductase activity-NRA-method) and identification; DST for first-line TB drugs on solid media; TB molecular methods (LPA and GeneXpert); TB microscopy (LED and/or ZN), trainings, supervision of state reference laboratories, panel proficiency testing, preparation of reagents for smear microscopy and research activities. These laboratories are in varying stages of completion and functionality. As of 2014, two of them are able to perform all the mentioned activities, one is under validation, another, fully equipped and ready to start the validation process. The remaining two will be fully functional by the end of 2016. The population coverage per ZRL is approximately 29 million persons. 

State laboratories (the third level) perform AFB smear microscopy and EQA for AFB with the exception of one state laboratory, DLHMH, Calabar which is also equipped to perform culture, DST for first-line TB drugs and molecular assays (LPA and GeneXpert). There is a plan to gradually upgrade the diagnostic services provided by all of the state labs to include culture, DST and molecular tests. According to this plan, a second laboratory located in FCT will be providing the services by 2015 and the number will increase to nine by 2020. The population coverage per laboratory at full implementation, with one laboratory per state, would be approximately 3,000,000 persons (still insufficient to cover the needs of the country for these diagnostic services). 

Peripheral laboratories are at the base of the pyramidal structure and are located within primary health centres, general hospitals, specialist hospitals and local government health clinics. Activities implemented at this level include sputum collection, sputum smear microscopy with conventional or LED fluorescent microscopes, recording/reporting of smear results, TB molecular diagnosis (GeneXpert in a few facilities only) and slide storage for EQA. Personnel requirements are for 1-2 lab staff for a workload of ≤ 25 smears per day. 

Zankli Medical Centre contributes to the diagnosis of tuberculosis, providing microscopy, culture and DST services and supporting research projects. It is integrated in the laboratory network through a memorandum of understanding with the NTBLCP.