Historical Background :
            Tuberculosis (TB) is a disease of great antiquity affecting mankind from very early times. Evidence of existence of tuberculosis has been found in the bones of Prehistoric man, found in  Germany. Those remains date  back to about 8000 B.C. Typical tuberculosis changes have been found in the spines of skeleton of ancient Egyptians dating from  about 2500 to 1000 B.C. In the year of 1882, Robert Koch discovered the tubercle bacilli, the  causative organism.

Present Scenario :
Tuberculosis is by far the  most frequently encountered mycobacterial disease affecting  human beings.     About 1.7 billion or one third of world's  population are, or have  been  infected  with Mycobacterium  tuberculosis.
              In India, 12-13 million  individuals are infected, with 50% of the Indian population, over the  age of  22 years are prone to tuberculosis. World wide an annual  addition of 2.5-3.2 million new  cases and 2.6-2.9 million deaths are reported, while in India an  annual addition of 2.5 millions new  cases and 0.5 million deaths (one  death per minute) are reported  (National Survey, NTI, 1991).  With 
the rapid spread of HIV-TB coinfection and multidrug resistance the epidemiology of this  disease is changing very fast. An  upward trend is seen in the developed countries and Africa. Three million people are infected with HIV TB worldwide.

 Global Emergency :

             Although tuberculosis is a  curable and to some extent  preventable disease, its diagnosis  sometimes, especially in  Extrapulmonary tuberculosis, HIV- TB, Childhood TB, Smear Negative  Pulmonary TB becomes difficult.  The WHO declared tuberculosis as a Global Emergency in 1993.  

Clinical Presentation of Tuberculosis :

             The incidence of pulmonary  tuberculosis is more frequent than  extrapulmonary form of  tuberculosis (EPTB). EPTB is increasingly recognized since last  decade because of the emergence  of AIDS. Tuberculosis is an air  borne disease,  being transmitted via respiratory route on inhalation  or ingestion of droplet nuclei  containing  varying    quantities of M tuberculosis bacilli. The man with active disease when coughs, sneezes or spits, aerosolizes  droplet nuclei. The risk of infection  progressing to disease varies with age, the risk being greatest in  children below 3 years, followed by young adult and the elderly people.

Pulmonary tuberculosis :

            This is the most common  form and affects the lung. The onset is usually insidious and  illness remains unnoticed by the patients for some time. It reaches   full extent with in few weeks. The extent of the disease varies from minimal infiltrates that produce no clinical illness to massive involvement with extensive cavitation and debilitating constitutional and respiratory symptoms. In the absence of effective therapy, this pursues a  chronic and progressive course  with growing bacterial colony. With the progression of pulmonary  disease the normal pulmonary  architecture is lost. The over all death rate of  untreated pulmonary tuberculosis approaches 60%.

Extra pulmonary tuberculosis :

             This occurs following haematogenous and lymphatic  dissemination of tubercle bacilli  from  primary pulmonary infection or  a reactivated focus elsewhere in  the body i.e. infected lymph node  etc. Number of tissues or different  organs may be infected such as :  

  • Tubercular lymphadenitis

involve the unilateral cervical nodes  especially those high in the neck  are more frequent in children. This  form of tuberculosis is the most  common form of extrapulmonary   tuberculosis constituting towards 30% of the total disease. As the disease progresses, sinus tracts are resulted. These may slowly respond to medication, rarely may require excision.

  • Bone & Joint tuberculosis

is more common in elderly,  although seen in all ages. The involvement is usually a late manifestation of haematogenous  spread of this disease. The site  most frequently involved is the vertebral body representing 36- 50% of the total bone and joint tuberculosis cases. Lumbar and low dorsal spines are commonly involved in older; high dorsal in young. The weight bearing bones / joints (knee, 12-15%) are also  involved. However any bone or  joint can be involved. The course of  disease starts from synovial  membrane, then inflammation  followed by demineralization and  caseous necrosis.   

  • Abdominal tuberculosis 

includes i) abdominal organ (GIT, liver, spleen etc.) ii) peritoneum iii)  lymphatics. The intestinal  tuberculosis can be related to  swallowing sputum tubercule bacilli  or the disease reactivation in peri  intestinal lymphatic tissue. The  ileocoecal area of small intestine is  the most common site (91%) involved. Peritoneal TB presents  with seeding of tubercles through out the peritoneal surface and occurs in ascitic (exudative) or plastic (adhesive or dry) forms. This form of TB is easily confused with other diseases such as  irritable bowel syndrome, alcoholic  cirrhosis etc. Usually the signs and  symptoms are vague and non specific, increases with age and patient presents with abdominal swelling, vague pain and alternate  diarrhoea and constipation.

  •  Meninges-CNS tuberculosis

is most common amongst infants, children with extrapulmonary  tuberculosis. The patient presents in  different stages: early fever,  headache, and malaise; later  confusion, seizures and coma. The  prognosis is related to stage.  


  • Genitourinary tuberculosis

is rare in young, more frequent  among females. This may involve  kidneys, ureters, bladder, testes,  epididymis, uterus, fallopian tubes  etc. This may complicate to early or  late obstructive uropathy, infertility  etc.

Pleurisy with effusion occurs  when the pleural space is seeded with the M tb. bacilli.  This may be acute or indolent; severe or  asymtomatic.

·                    Tuberculous pericarditis  represents as extension of pleurisy. This causes, dyspnoea and vague discomfort. Exudative effusion occurs and patients present with fever and pericardial pain, chronic obstructive pericarditis being its last sequele.  

·                    Disseminated tuberculosis is most frequent in very young or old.  Chest film abnormalities may lag and patient presents with progressive fever. Early therapy is vital.



            Early diagnosis of tuberculosis is important both to individuals and to community, and is very crucial yet difficult to achieve. Presently the diagnosis of tuberculosis largely depends upon clinical, radiological, cytological & bacteriological examinations. Though the direct microscopy of sputum for acid fast bacilli (AFB) is reliable for pulmonary tuberculosis, it is not that sensitive, limitations being, it may give false negative results and require a high degree of bacillary load of 50000 bacilli / ml of sputum and is subject to inherent errors like contamination. Other demerit is that it is positive in open cases only. Thus it is not helpful in extrapulmonary form of tuberculosis and in childhood tuberculosis where sputum is not available. The culture method is cumbersome and time taking, requires 6-8 weeks for positive results. The radiological examination is non specific and not suitable for field studies in developing countries, like India. The tuberculin skin test is not reliable in discriminating active form from non active tuberculosis. Even the new techniques such as PCR, DNA Probes, RFLP, BECTEC system, etc. for early diagnosis of tuberculosis are no doubt are sensitive and help rapid diagnosis, but still do not find their way into routine diagnosis and more over not cost effective and practical in developing countries. Thus, there is a search for alternative test which will stand with its merits in vigorous clinical trails. Serodiagnostics have attracted considerable attention of the Investigators.




            SEVA TB ELISA (IgG & Ag) system based on the detection of tubercular IgG antibodies and antigen in tuberculosis has been developed and explored in several ways at this institute. The detection of IgG antibody (titre 1:600 and above) by indirect ELISA against SEVA TB ES 31/41 antigen in pulmonary and extra pulmonary tuberculosis suggests active tuberculosis infection. Free tubercular & Immune complexed antigen (IC-AG) is detected using affinity-purified anti ES-31 antibody by sandwich ELISA. A serum with an antigen titre of 1:300 and above is considered for positive reaction. The combination of antibody, free and IC-Ag detects 100% cases of pulmonary TB. The test is quite helpful in childhood tuberculosis where it is difficult to obtain sputum sample. This test has been found useful in clinically suspected and anti tuberculosis therapy (ATT) responded cases, which were negative for bacterial examination. This test has also been useful in confirming tubercular aetiology in extra-pulmonary tuberculosis (bone & joint, abdominal, CNS-meninges, lymph node, genito-urinary etc.)


Antibody detection by indirect penicillinase ELISA and Antigen detection by Sandwich ELISA:


            The antibody detection test is based on the detection of spec-ific IgG antibody to purified culture filtrate antigen of Mycobac-terium tuberculosis H37Ra (SEVA TB ES  31/41) by indirect penicil-linase ELISA. The ES-31/41 antigen co-ated CAM sticks are incubated with diluted human sera followed by addition of antihuman IgG penicill-inase conjugate. After washing, the enzyme reaction is detected using starch-iodine-penicillin 'V' substrate. The disappea-rance of blue color of substrate indicates the presence of antibody to ES-31/41 antigen. In a study on antibody detection to SEVA TB ES-31 has given a sensi-tivity of 92% compared to sputum AFB positivity of samples tested and a specificity of 95% in pul-monary tuberculosis (Banerjee et al 2001). Antibody detection to ES- 41 was found to be quite useful in diagnosis of bone & joint and abdominal tuberculosis.

The free and IC-Ag dete-ction is done by sandwich ELISA. The CAM sticks sensitized with affinity purified goat antibody aga-inst M.tb ES-31 antigen are incubated with appropriate test sera followed by addition of penicillinase labeled anti ES-31 antibody. The positive reaction is detected by disappearance of blue color of the substrate. Free antigen and IC-Ag detection assays have given sensitivity of 80% & 72% respectively and specificity of 95% & 97% respectively. This test is quite helpful to detect tubercular IgG antibodies in extra pulmonary tuberculosis cases viz; tubercular lymphadenopathy(88%), tubercular meningitis (90%), abdominal tuberculosis (82%), bone & joint tuberculosis (85%), genitourinary tuberculosis (71%) etc. (Banerjee et al, in communication).




            A follow up study of immune status during the course of ATT of tuberculosis patients showed an initial rise of tubercular antibodies in the first month of treatment followed by gradual decrease in the titers by the end of treatment. Similarly circulating tubercular antigen levels were also found to be decreasing gradually with the treatment. At the end of six months of ATT, about 75% showed the absence of circulating tubercular antigen. Thus presence of antigen may be used as a marker for elimination of tuberculosis infection as well as compliance of the patients with ATT.



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