TB LABORATORY SERVICES AND ITS QUALITY CONTROL
Ms. Akiko FUJIKI
The Research Institute of Tuberculosis, JATA
[□] IMPORTANCE OF TB MICROSCOPY IN NTP
1) Significance of bacteriological examination in NTP
The principle of TB control program is clearly stated as follows by WHO 9th technical report in 1974;
"The object of tuberculosis control is to break the chain of transmission of infection. This can be achieved by detecting the source of infection as early as possible and rendering them noninfectious by chemotherapy. Transmission is maintained in the community particularly by subjects whose sputum is so heavily positive that tubercle bacilli can be detected by smear microscopy."
The priority of tuberculosis control is to detect smear positive cases since they are the greatest risk to the community and WHO recommends that the diagnosis of tuberculosis is based on direct sputum smear microscopy.
2) Role of bacteriological examination in NTP
The laboratory plays a key role in diagnosing new cases (case-finding) and in monitoring patient's response to chemotherapy in the NTP (follow-up).
TB laboratory can also assist in selecting effective regimens for the patients who failed initial treatment and in epidemiological studies for the improvement case detection and cure rate.
[□] LABORATORY NETWORK
3) Laboratory network
The laboratory network should be covered throughout the country efficiently and be organized according to the daily workloads, availability of facility and trained personnel, financial resources, transportation facility and geography of the country to be accessed by people.
Three kinds of laboratories are recommended to organize TB laboratories.
Peripheral level (District level or below)
The peripheral level of laboratory is restricted to sputum smear microscopy with Ziehl-Neelsen staining method or just sputum collection and smear preparation. The prepared slides are just forwarded to the laboratory where smear microscopy is available.
One microscope and one or two microscopists, trained in ZN staining method and microscopy cover 100,000 to 200,000 population.
Intermediate level (Regional or Provincial)
This level of laboratory covers a population between 500,000 and two million. The functions are routine microscopy by ZN or fluorescence staining method, training of microscopists, reagents preparation, quality control and supervision on sputum smear examination to the peripheral level of laboratory. Sometimes culture examination is available. One to two microscopists are involved in sputum microscopy and two or three laboratory technicians are required for other duties except microscopy.
Central level (National)
This is the specialized TB reference laboratory. This should be capable of doing culture examination, drug susceptibility test, identification test of TB and MOTT. And also this level of laboratory is responsible for training, reagents and equipment supply, quality control and operational research. At least four laboratory technicians are required.
[□] DETECTION METHOD OF MYCOBACTERIA
4) Detection method
There are mainly three types of detection methods for mycobacteria, as it is shown here. Direct sputum smear examination, culture examination and DNA examination.
Smear examination is simple, quick, cheap but less sensitive compared to culture examination.
Culture examination is a complex and expensive which requires skilled technique and takes a long time to get the result.
However, it permits to the detection of small number of TB bacilli present in the clinical specimens.
It also obtains living bacilli to perform further detailed examination.
A variety of DNA examination or rapid detection method based on molecular biology has been developed recently such as PCR, the use of specific DNA-probes, early detection of growth by CO2 production (BACTEC) or O2 consumption (MGIT) and so on.
Many people are interested in these techniques; however, their feasibility in developing country is in question. (they are not encouraged to apply in developing countries.)
Because 1) reagents and equipment are expensive, 2) operation of the procedure techniques are complicated even though kits are commercially available, 3) well-trained personnel are required, 4) dead bacilli or living bacilli can not be distinguishable.
[□] DIFFERENCES OF TB EXAMINATION
5) The cost of TB exam.
The cost of TB examination in Japan is shown here.
