TUBERCULOSIS – DIAGNOSIS AND TESTS

Diagnosis of Tuberculosis
Tuberculosis is a one of the most spread communicable disease in India. Tuberculosis is considered the “BAROMETER of SOCIAL HEALTH”. Prevalence of this disease in the community is an indication for health of the population in the society.
This disease has been a topic of concern for government on India for long. RNTCP (Revises national tuberculosis program) now named as NTEP (National Tuberculosis Elimination Program) is a program setup by government which regulates the system of diagnosis and treatment In India. Thanks to this program, today we can diagnose much more patients as compared to earlier.
Signs and symptoms of Tuberculosis include-
Fever
Cough
Night sweats
Weight loss
Any of the above symptoms for a period of 2 weeks or more may indicate lung tuberculosis.
Over the time, with development of tuberculosis, diagnostic mechanisms for tuberculosis have evolved greatly. This has helped in diagnosing tuberculosis more rapidly and accurately.
Tuberculosis has a capacity to spread (disseminate) to other organs as well. It can spread to other organs such as intestines, spine, kidney and others.

Diagnosis of Lung Tuberculosis
In India, according to NTEP, diagnosis is done mainly on the basis of clinical basis and-
Radiological investigations – Chest X ray
Sputum genotypic and phenotyping- CB-NAAT.
In India, the diagnosing system is set up in such a manner, that even the individual staying in rural areas is not left out.
Hence for diagnosis of tuberculosis, X ray machines and CB-NAAT machines are present in every centre right from public health centres to district hospitals and higher medical colleges.
A patient who comes with any of the above complains is first tested using CB-NAAT and X-RAY. If the patient comes out positive in CB-NAAT test is a confirm tuberculosis patients.
In case if the CB-NAAT comes negative, but the physician is doubtfully of the result or if the X RAY shows typical changes in lungs, he or she is tested further using higher investigations. In such cases he/she is referred to specialists at higher testing centres. These higher investigations include tests such a as LPA (Line Probe Assay).

Diagnosis of DRUG RESISTANT TUBERCULOSIS (DRT)
Over the time, Tuberculae bacteria have become resistant to various medications used for the treatment. This becomes a big obstacle in treating patient and making him/her free of tuberculosis.
Diagnostic tests for drug resistance is done if the patient is not responding to the medications or has come in contact with a patient who was resistant to drugs.
CB-NAAT is done using sputum of the patient. This not only tells about the presence of bacteria in sputum but also tells about the Rifampicin drug resistance. Rifampicin is an important drug of the first line treatment drugs. The Tuberculae bacteria have started to show resistance against Rifampicin. Hence, CBNAAT play a very important role as diagnostic test for tuberculosis.
For testing of resistance of Tuberculae against any particular drug, Line Probe Assay (LPA) are performed. This shows whether the tuberculosis present in the patient is resistant to any medication or not.
Such investigations help in giving the correct and required treatment to the patient.

DIAGNOSIS OF ABDOMINAL TUBERCULOSIS
Tuberculosis may or may not be present only in lungs. It has a capacity to spread to other organs such as abdomen, kidney in form of secondary infection or reactivation.
Apart from lungs, tuberculosis can primarily affect intestines. The most common site for abdominal tuberculosis is near the junction of ileum and caecum. This mostly gives out symptoms such as constipation and abdominal pain.
Diagnosis abdominal tuberculosis is done using BARIUM STUDIES or BIOPSY
A barium liquid is consumed by the patients. This helps in understanding the level of obstruction caused by abdominal tuberculosis.
In order to get the confirmation of abdominal tuberculosis BIOPSY is taken by doing COLONOSCOPY. Here a scope (tube with camera) is passed through the anus and a section of the infected site is taken. Culture of this specimen is done which shows the exact result about the specimen.
Further tests may be required by the physician to understand the depth of spread or other medical reasons.

List of Diagnostic test FOR LUNG TUBERCULOSIS
Sputum microscopy
Disadvantage – less sensitive
this use microscope to detect mycobacterium tuberculosis and can detect 10,000 bacteria in 1 ml of sputum
Fluorescent microscopy-
Using Rhodomaine and Auromine stains
Disadvantage – costly
This is one of the methods which might be used in testing centers in near future
LED microscopy
Sputum culture
On culture medias such as Lowenstein Jensen, Dorse, Middle Brook etc.
Advantage – more sensitive than the microscopy – can detect 10-100 bacteria
Disadvantage – takes 8 weeks to show results
Radiology
Chest X ray
X rays are located even in rural destinations. Hence these form a strong base of diagnosing lung tuberculosis in rural and town cities
Automated methods
Includes BACTEC 460 and BACTEC MGIT
Advantage – faster results (in 2-3 weeks)
Geno-typing and Phenotypic methods
PCR
CBNAAT (cartridge based nucleic acid amplification technology)
Is currently the basis of diagnosing a patient as tuberculosis according to NTEP
Advantage- also tells us about the rifampicin sensitivity
TrueNAAT
Line probe assay
These are mostly used in cases where CBNAAT is negative but the physician is doubtfully or X ray shows relevant changes.
SEROLOGICAL METHODS
These have low sensitivity and low specificities
Hence are not used for diagnosing tuberculosis in India
These include-
IGRA (interferon gamma release assay)
Mantoux test
This was used much earlier in India, where a patient was injected a small amount of solution and that site was observed for changes after 2 or 3 days
Not used in India for diagnosis purposes

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