Annually, Tuberculosis (TB) affects 9.4 million individuals and cause 1.3 million deaths worldwide. EPTB is defined according to WHO classification criteria as an infection by M. tuberculosis which affects tissues and organs outside the pulmonary parenchyma [1]. In India, EPTB constitutes 10-15% of total TB cases which primarily involve the pleura, lymph nodes, gastrointestinal tract and other organs with a significant case mortality rate (25 to 50%) [2]. Available information revealed that the most common sites of EPTB was lymph node followed by pleura and abdomen. It can occur as an isolated form or along with pulmonary form of TB and also can affect multiple organs at one point of time. Approximately 5% of the incident TB cases have co-morbidity with HIV, though this proportion varies depending on the HIV prevalence of the population. Present as the co-morbid form with pulmonary TB, EPTB patients have high probability of death within six months of diagnosis (Sharma SK 2005, Swaminathan S 2000.In resource limited countries with lack of diagnostic facilities, identification of EPTB cases relies significantly on high index of clinical suspicion.Extrapulmonary tuberculosis is mostly underdiagnosed due to high rates of smear negativity in these cases. As the extrapulmonary sites are mostly smear negative, it is believed that these cases are less contagious and thus these are not a priority in the campaigns done by national TB control programs. [3-4] Early diagnosis and timely treatment is required in these cases to prevent further spread and reduce the mortality. Fine needle aspiration cytology and Z-N staining is an initial diagnostic tool in resource poor countries. It is a rapid diagnostic technique but has very lowsensitivity due to its paucicellular nature. [5]. The phenomenon of a “paradoxical reaction” (PR) during the treatment of tuberculosis (TB), in which existing disease may worsen or new lesions appear, has been recognised for many years [6-7]. It is unpredictable in its timing (occurring anything from a few days to many months after the start of antituberculosis chemotherapy) and in its duration and severity. Recognition of deterioration resulting from PR rather than from treatment failure, drug resistance or another infection can therefore be difficult. Most reported cases have complicated the treatment of lymph node or cerebral disease, with enlargement of nodes seen in approximately 30% in one large series [8].         

CBNAAT and Line Probe Assay introduced in 2009 and scaled up from 2012 onwards, have ensured that rapid molecular diagnostics are available throughout the country. The Truenat TB test is a new molecular test that can diagnosis TB in one hour as well as testing for resistance to the drug rifampicin. There are now several different assays which have expanded the capability of the test. DrBalramBhargava, the Director General of the Indian Council of Medical Research, said that this endorsement of the technology by WHO would enable low and middle income countries to procure TrueNat for tuberculosis diagnosis and Rifampicin resistance, so supporting the elimination of the disease in developing countries [9]. WHO also said that the evidence reviewed supported the continued use of Xpert MTB/RIF and Xpert Ultra as initial diagnostic tests for pulmonary TB in patients of all ages.

The standard smear microscopy test has limitations. It usually finds it difficult to diagnose TB when the bacterial load is less than 10,000 per millilitre of the sputum sample, giving erroneus negative results for some patients. 

Line probe assay and CBNAAT are molecular method for rapid diagnosis of Tuberculosis [10].The test works by the rapid detection of TB bacteria using the polymerase chain reaction (PCR) technique.The machine looks for the DNA specific to the TB bacteria. If the machine detects it, it then uses PCR to copy (amplify) small segments of DNA and this DNA can then be used in many different laboratory procedures.Any resistance to rifampicin (RR) is detected by doing a second RTPCR (Reverse transcription polymerase chain reaction). It takes about 25 minutes to do the DNA extraction. It takes another 35 minutes to diagnose TB. It takes an additional one hour for testing for rifampicin resistance [11] Doing First line Line Probe Assay also called Genotype MTBDR plus detects Rifampicin and Isoniazid resistance. LPA detects rifampicin resistance by detecting rpoB mutation and isoniazid resistance by detecting both katG and inhA mutation.

The study was conducted by analysing data of last three cosecutive years from 2019-2021 in tribal district, Kinnaur of Himachal Pradesh. Out of all TB cases notified data of EPTB cases diagnosed, type of EPTB including method of diagnosis was analysed by simple statistical test.

The skin of the patient, over the suspected lymph node to be aspirated was cleaned with betadine or spirit. The lymph node was then fixed between the thumb and index finger of left hand, then 18 gauge needle attached to 10 ml syringe was introduced into the lymph node. Vaccum was created in the syringe by pulling the plunger and needle was carefully moved in all directions to dislodge the material. The sample for CBNAAT was collected in Falcon tube and sent to lab immediately. USG guided pleural tap or aspiration/ biopsy of tissue was also collected under aseptic technique and sample processed in similar fashion. Results were reported as positive or negative for M. tuberculosis as CBNAAT gives semiquantitative estimate of the concentration of bacilli as defined by the Ct (cycle threshold) range (high, <16, medium, 16-22, low, 22-28, very low, >28). Assays that are negative for M. tuberculosis and for the internal control are reported as invalid assays. Rifampicin resistance results were reported as susceptible, resistant.

Observations

The following observations were made

Age wise distribution of patient shows no age group is spared in EPTB over last three years even when age group kept at 5 years. Total patients of EPTB were 79, 80 and 67 in year 2019, 2020 and 2021 respectively at Regional Hospital ReckongPeo (RH). 

Maximum number of patients were seen in age group 20-25 followed by 25-30 years. 2021^* data upto December 20^th Table 1.

Male patients of EPTB diagnosed were more in comparision to females in all three years showing male predominance.44 55% M :35 45% in 2019 and least in 34 51%:33 49% in 2021 Table 2.

In 2019 only 5 (6.7%) patients out of 79 were diagnosed at RH, 25 (31.2%) patients out of 80 in year 2020 and12 (17.9%) out of 67 patients diagnosed with EPTB were of this year (Table 3).

Year wise distribution of PTB and EPTB patients in district Kinnaur shows EPTB were 79 35.7%, 80 41.6% and 67 37.6% in 2019, 2020 and 2021 respectively, Total cases PTB+EPTB were 221, 192, 178 showing declining trend from 2019 to 2021 Table 4.

75 33% out of 226 cases were of pleural effusion followed by 50 22% of others, 37 16.7% of lymph node (LN), 31 13.7% abdominal (ABD), 13 5.75% of spinal, 7 3% each of genitourinary (GU) and tubercular bacterial meningitis (TBM) and lastly1 2.6% of bone tuberculosis Table 5.

Total 4 patients of pleural effusion diagnosed in 2019 at RH. CBNAAT was done in 1 patient and 1/1 100% case detected by CBNAAT. 2 20% out of 10 cases of pleural effusion in 2020 were confirmed by CBNAAT. 1 12.5% out of 8 of pleural effusion diagnosed by CBNAAT in 2021. Overall 4/19 21.05% of pleural effusion were diagnosed by CBNAAT in three years. 5/5 100% cases of lymph node tuberculosis were detected by CBNAAT in 2020. 1/1 100%, 4/5 80%, 2/2 100% of samples from other site were confirmed by CBNAAT in 2019, 2020 and 2021 respectively. 16 47% Out of 34 cases were detected by CBNAAT Table 6.

22 29.3% out of 75 patients of Pleural effusion were detected at RH. 4 19% out of 22 at RH and 0 cases out of 53 outside district CBNAAT was basis of diagnosis in pleural effusion.Overall 34 15% of 226 cases CBNAAT was basis of diagnosis Table 7.

Table 1: Yearly Age Wise Disribution of Patients

Table 2: Yearly Distribution of Patients Gender and Percentage Wise

Table 3: Year Wise Distribution of EPTB Patients Diagnosed at RH/Outside District with percentage Age RH Diagnosis

Table 4: Year Wise Distribution of PTB and EPTB Patients with % in District Kinnaur

Table 5: Yearly Site Wise Distribution of EPTB Patients with Cumulative Percentage Distribution

Table 6: Total CBNAAT year wise EPTB site wise and percentage detected at RH

Table 7: Basis of Diagnosis of EPTB Cases Site Wise of Disttkinnaur in Last 3 Years at RH and Outside

In our study age distribution of patients over three years shows maximum number of patients were in the age group 20-25 years followed by 25-30 years. EPTB was observed to affect the population of economically productive age group of 15 to 35 years than extremes of age similar to our study. However, no age group is exempt from EPTB in our study showing prevalence of disease in society. Population of Kinnaur is least densely populated in India and tribal district have already been appreciated at national level for achieving goals towards TB elimination. Covid -19 have been debated to push back TB elimination goals, impact of which is difficult to predict in district as TB cases are showing declining trend though marginally.

Sex distribution in our study showed slight male predominance. The global reports on TB by WHO found a higher incidence of the disease among males [12]. In 2019 at RH only 5 6% of 79 cases of EPTB were diagnosed rest outside. Overall 42 18.5% of all 226 EPTB patients were diagnosed at RH in last three years. Diagnosis of EPTB requires multispeciality coordination and workup, availability of which is remote possibility in rural areas which explains small propotion of EPTB cases diagnosed at RH. Total EPTB cases notified in district were79 36%, 80 42% and 67 38% in 2019, 2020 and 2021 respectively. Globally also there is increasing trend in EPTB cases.

Site-specific distribution of cases shows maximum number of cases were of pleural effusion 21, 27 and 27 in 2019, 2020 and 2021 respectively. Overall 75 33.1% out of 226 cases of EPTB were pleural effusion followed by 50 22% of others, 37 16.7% of LN, 31 13.7% ABD, 13 5.75% of spinal, 7 3% each of GU /TBM and lastly1 2.6% of bone tuberculosis. Studies reported that the pulmonary involvement ranges from 20.0% to 50.0% in EPTB cases.

On analyzing data of patients at RH 4/19 21.05% of pleural effusion were diagnosed by CBNAAT in three years. 5/5 100% cases of lymph node tuberculosis were detected by CBNAAT in 2020. 1/1100%, 4/5 80%, 2/2 100% of samples from other site were confirmed by CBNAAT in 2019, 2020 and 2021 respectively. 16 47% out of 34 cases tested were detected by CBNAAT Table 5. Overall 34 15% out of 226 EPTB notified cases in Kinnaur and 16 38% of 42 diagnosed at RH over last three years were detected by CBNAAT.

CBNAAT is a sensitive, effective and rapid diagnostic tool for EPTB. It can diagnose more number of smear negative as well as multiple drug resistant tuberculosis very early. This provides an extra edge for tubercular management as these undiagnosed cases are of global concern. This should be used as an initial diagnostic tool for these cases. Thus the present study highlights the impact of CBNAAT in diagnosis of EPTB e.g tubercular lymphadenitis cases in resource poor countries like India, where tuberculosis is so prevalent. With early detection of these patients out pocket expenditure on invasive diagnostic tests and time is saved by avoiding repeated follow up visits.

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