TUBERCULOSIS LABORATORY SERVICES
by
Dr Sang Jae Kim
Korean Institute of Tuberculosis
Seoul, Republic of Korea
?. ROLE OF LABORATORY IN THE NATIONAL TUBERCULOSIS PROGRAMME
The laboratory plays a key role (1)in diagnosing new cases and (2) in monitoring patient's response to chemotherapy in the National Tuberculosis (TB) Programme (NTP). TB laboratory can also assist (3) in selecting effective regimens for the patients who failed initial treatment. Treatment response cannot be evaluated by radiography but only by sputum status. whether or not tubercle bacilli are continuously excreted.
As the case-finding programme aims at recovery of the patients from TB and prevention of new infection, so NTP must stress on screening of infectious source cases in the community. The major infectious sources are of course heavy bacillary excretors who can be easily diagnosed by direct smear microscopy (DS). Therefor, smear microscopy is a basic, priority procedure to be organized in NTP. It will render a great impact on the control of TB particularly in highly prevalent countries where most of the notified cases are smear positives usually left undiagnosed for long period of time.
Culture is a complex and expensive procedure with requires skilled technique and takes a long time to get result. However it permits to detect small number of tubercle bacilli present in the clinical specimens and most of the cases so found will eventually develop to the infectious cases if left untreated. Therefore it is highly recommended to organize culture facility in NTP along with smear microscopy in the countries that can afford it.
Drug susceptibility testing (DST) provides an important epidemiological information such as prevalence of initial or acquired drug resistance and serves as a guide to selection of effective re-treatment regimens.
A variety of advanced technology based on molecular biology has been developed recently and wait for a thorough clinical evaluation under the various settings.
?. ORGANIZATION OF LABORATORY SERVICES
The laboratory services of NTP should be organized into several levels according to the health delivery system, daily workloads, availability of trained personnel and facility, financial, resources transportation facility, and geography. Hence each country must organize and develop the laboratory network suitable to the conditions and be able to cover the whole country efficiently.
At the most peripheral health institutes where no laboratory exists, only sputum (or other specimens) collection is performed and the specimens are transported to the small laboratories instituted in the district hospitals or in the health centres where they are to be examined by DS microscopy only. This type of peripheral laboratory is usually multipurpose and occupies 1-2 rooms. If the specimens are to be cultured or require DST, they should be transported to higher level laboratories such as intermediate or central laboratory. The central laboratory is usually organized in the capital city so as to serve as a capital city laboratory on the one hand and to serve as the national reference laboratory on the other hand by supervising the peripheral and intermediate laboratories, by performing identification and DST in addition to the tasks of lower level laboratories, and by providing training of laboratory personnel in all levels; equipment specification: standardization and quality control of all the laboratory procedures in use: planning and evaluation of programme: and basic and operational researches. As though it is desirable to decentralize the laboratory services in order to make easily available and convenient to patient management, the decentralization, however, requires more money and intensive supervision and quality control.
At the beginning of organization, the central laboratory may have a direct responsibility of supervision and quality control of the peripheral laboratories. However, increase of the number of peripheral laboratories makes a central laboratory unable to supervise them efficiently and this situation urges to establish intermediate laboratories, capable of supervising affiliated peripheral laboratories and of doing culture and smear microscopy of specimens received.
All efforts must be devoted to provide a fast and accurate laboratory services, which are most efficient and convenient to the case-finding and case-management. Hence different levels of laboratory must perform the procedures most efficient to the designed purpose and suitable to their workload and capacity, otherwise it will be unavoidable to waste invaluable resources. The fast result is desirable for a quick diagnosis and commencement of treatment. However the fast results must not sacrifice accuracy and reliability of examination.
