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COMPARATIVE STUDY OF SENSITIVITY OF DIAGNOSTIC TESTS FOR TUBERCULOSIS IN CHILDREN
JG SALUJA*, MS AJINKYA**, BHAVNA KHEMANI***
*HOD and Associate Professor; **Associate Professor; ***Chief Pathology Technician, CMPH Medical College and Shri. Mumbadevi, Hom. Hospital, Vile Parle, Mumbai 400 056.
Childhood tuberculosis is believed to be on the rise worldwide, because of persisting inability to confirm the diagnosis. A study was therefore taken up based on criteria with acceptable sensitivity, specificity and positive value.
Total 75 children of diagnosed cases of tuberculosis were registered from various TB clinics and Shri Mumbadevi Hom. Hospital. Three groups of patients namely A (1-5 years), B (5-10 years), C (10-14 years) were formed and diagnosis was based on the following parameters : X-ray chest, MT, ESR/Haematology, CRP, Gastric lavage, Adenine deaminase, TB IgG. The results were tabulated in to various graphs as mentioned in the test. The sensitivity of various test against the gastric lavage was done. The statistical significance of gastric lavage AFB positive is 70.3% of patients and its 'P' value is significant over ESR test, TB IgG test, ADA test. Therefore gastric lavage test can be considered as one of the diagnostic test for the suspected or problematic cases of childhood tuberculosis.
INTRODUCTION
According to the review of the global tuberculosis by WHO.[1] India comes under the group of high prevalence countries with annual risk of tuberculosis infection ranging between 1-2.5%. Due to a higher prevalence in children are at a higher risk of contracting the disease from the infected pool of adult cases.
Childhood tuberculosis is believed to be on the rise worldwide, because of persisting inability to confirm the diagnosis. A large number of children die of undiagnosed tuberculosis.
The interaction of HIV and tuberculosis is becoming evident in childhood also because of HIV co-infected mothers are capable of passing tuberculosis to their children congenitally.
Diagnosis of tuberculosis among children poses technical and operational challenges because of vague and non-specific symptomatology, difficulty in getting sputum sample for testing complexities in the interpretation of tuberculin tests results and chest X-ray and lack of single simple cheap and reliable test for making a diagnosis.[2]
There are consequently technical and operational constraints in organizing disease surveys in this paediatric age group, which may explain the paucity of epidemiological studies in this respect.
In late 70's the prevalence of radiological positive disease among children was estimated to be 0.3%.[3]
Several criteria for diagnosing childhood tuberculosis based on clinical features and basic investigations have been recommended by WHO.[4]
A study was therefore taken up; based on criteria with acceptable sensitivity, specificity and positive value. Several factors like clinical features, family contact history, X-ray examination, tuberculin testing, TBIgG, CRP, ESR and gastric lavage, etc. were considered in this study.
MATERIAL AND METHODS
The registered children were subjected to
*Elicitation of history and clinical examination
*Investigations
Three groups were formed
A) 1-5 yr .
B) 5-10 yr.
C) 10-14 yr.
*H/O symptoms suggesting tuberculosis like prolonged fever, failure to thrive, persistent cough or P/H of hospitalization for tuberculosis.
*Assessment of nutrition by Quetlet index method[5]
Undernutrition was assessed by adopting the formula
Weight in Kg/ Ht. In sq. cm X 100
Undernourished children were also considered in the study.
-Evidence of lymphadenopathy
Discrete discharging sinuses
-Vaccination for BCG
BCG Vaccinations
Group A Vaccinated Not vaccinated (no scar) Group B Vaccinated Not vaccinated (no scar) Group C Vaccinated Not vaccinated (no scar)
*Subsequent investigations were also done in each of the group of children
Viz. -CBC, ESR
-Mantoux test
- X-ray chest
- sputum for AFB/Culture
- Gastric lavage for AFB
- TBIgG
- Adenine deaminase .
Total 75 children of diagnosed cases of Tuberculosis were registered from various TB clinics and Shri Mumbadevi Hom. Hospital (Pead. Dept) (From January 1999 to December 2000)
Diagnosis was based on the following parameters
*X-ray chest
*MT
*ESR/Haematology
*CRP
*Gastric Lavage
*Adenine Deaminase
*TBIgG
Total number of patients = 75
Gastric lavage AFB ZNCF modified.
The following parameters are considered for the statistical study to bringforth value of "Gastric Lavage" as a sensitive test.
In all the +ve Tuberculosis patients we compare the sensitivity of
i.Lavage test with ESR test
ii.Lavage test with MT test
iii.Lavage test with CRP test
iv.Lavage test with TBIgG test
v. Lavage test with ADA test
Age Group. A 1-5 yrs
Age Group. B 5-10 yrs
Age Group. C 10-14 yrs
N = Normal; H = High; INT = Borderline; MT+ve = More than 10 mm erythema and induration; MT -ve = No induration or erythema or only erythema; ESR = Western Green method; TBIgG = ELISA > 225 units positive; ADA = Adenine deaminase (serum N=70); H = Hilar lymph nodes; MZ = Mild zone; LZ = Lower zone
Let us assume null Hypothesis where lavage test has significance. Applying the formula.
Z=
P1x (100-P1)+P2x100-P2
P1 = No. of AFB +ve Gastric Lavage tests of all the age groups.
P2 = No. of (H) ESR/ (+ve) MT/(H) CRP/(H) TBIgG/(H) ADA tests of all age groups.
Z Value = 1.645 or > Equates to P [0.05 which give the sign of the Test]
AFB +ve with MT positive in group A, B, C.
AFB +ve with ESR in group A, B, C.
AFB +ve with CRP positive in group A, B, C.
with ESR, CRP, MT.
DISCUSSION
BAL specimen may be responsible for low yield of mycobacterium because of local anaes thetic agent[6] used for bronchoscopy. That is why Somu, et al found that gastric lavage was superior to bronchoalveolar lavage (BAL) fluid for isolation of mycobacterium specimen. Clinical utility of rapid tuberculosis detection in gastric lavage sample by PCR[7] may be much superior because of sensitivity and specificity.
ESR measurement[8] has more limitations when it is used as a screening test for the presence of disease. Any screening test should be highly sensitive (showing few false negative) and highly specific (showing few false positive). ESR is not very sensitive test for the presence of disease.
Significant numbers of patients with malignancy, infection, or inflammatory disorders have normal ESR. In patients with marked elevated ESR there is high specificity of disease so this measurement may have some use as a sickness index.[9] A different approach to ESR should be taken and conclude with a combination of clinical evaluation and ESR as a sickness index can be taken and can conclude that with a combination of clinical evaluation and ESR measurement it is possible to identify a group of patients in whom the likelihood of disease is quite or reasonably high, then one can reduce the number of patients undergoing unnecessary investigations.
ESR has a low place as a screening tool in symptomatic individual, it may be useful in group of patients in whom clinical evaluation has given rise to moderate suspicion of the presence of disease. There are no significant differences in ESR values for children between either age or size of tuberculin skin test reactivity. In our study ESR was high in children with tuberculosis but more than 1/3rd had normal ESR. Thus it would seem to be little of value using ESR as a diagnostic test in childhood tuberculosis. C reactive protein[10] (CRP) measurement has been suggested to be a superior test for monitoring the disease activity. CRP is a measure of short-term change in acute phase response. Useful for monitoring the remission of acute inflammation. Of ESR is more complimentary rather than alternate tests.[11]
A dissociation of cell mediated immunity (CMI)[12] and delayed type hyeprsensitivity (DTH) is described in tuberculosis and it has been suggested that cellular type immune response is involved.
CMI seen as beneficial host response and DTH as immunological reaction that caused caseous necroses.[13] Although Mantoux test +ve host with good CMI as well as poor CMI could arrest bacillary multiplication. The host with good CMI might recover while the host with poor CMI might suffer excessive tissue destruction. There are two cell type profiles; e.g. one group may have tuberculin reactive good CMI and the other tuberculin reactive poor CMI.[14-15]
It has been observed that two mechanisms of cell mediated response referred to as Listeria type and Koch's type could occur in infection with mycobacterium. The Listeria type[16-17] response is thought to produce protective immunity, healing occurs in proportion of tuberculosis patient without treatment, which might be due to development of good CMI in some of these patients.
The early attempts to diagnose TB serologically were based on crude or partially fractionated antigen and invariably there was a high overlap between the results on the tests on proven cases of TB on healthy control subjects. These tests were practically unhelpful in those very cases where a good diagnostic test was most needed in every case. Purified antigen[18] like antigen 5 or antigen 6 have also proved disappointing results. The possible reason for this is cross reactivity between many of the immunogenic mycobacterium constituents and the presence of heat shock protein in the antigenic preparation.[19]
Wilkins and Ivanylal[20] could detect 73% of cases of extra pulmonary TB and 70% of smear -ve pulmonary tuberculosis. Dawart et al[21] investigated specific IgG response after BCG vaccination antibodies to a P64 antigen increased significantly following vaccination but no increase was observed in antibodies to P32 antigen. Levels of P64 IgG are high enough to facilitate a serological differentiation from tuberculosis.
Von Booren et al[22-23] reported that patients with high tubercular pleural effusion, anti P32 antibodies were generally higher in pleural fluid than in serum.
The sensitivity of the tests was 85.2% and the specificity was 95.9%. Thus it can be concluded that assays for IgG antibodies were superior to that of protein antigens for the detection of serological evidence of tuberculosis.
Adenine deaminase is an aminohydrolase that catalyses the deamination of adenosine to inosine. Its biological activity is related to proliferation and differentiation of lymphocytes.[24-26] Elevated levels have been detected in effusions due to peritoneal, meningeal, pleural, and pericardial. However it was found to be non-specific in our study which was done from serum of tuberculosis patients.
Lastly we suggest that more and more gastric lavage specimens to be collected to rule out tuberculosis, since the sputum yield from the children of various groups are difficult.
However PCR (polymerase chain reaction) and LCR (ligase chain reaction) results are available in three days as compared to a culture, which takes six weeks; but the important fact is that even the smallest amount of contaminating DNA can be amplified, resulting in misleading results.
In a few case reports when different samples from the same patient were tested, positive results were obtained intermittently.
For the above-mentioned reason sometimes the above mentioned PCR and LCR may give false positive results. i.e. why the smallest unsophisticated test may be sufficient enough to diagnose childhood tuberculosis, because of its good reasonability and good reproducibility, as compared to highly sophisticated tests; e.g. Initially described PCR protocols could detect as low as 10 bacilli in the sample. Recent modifications have enabled us to detect DNA extracted from a fraction of bacilli to be detected after suitable amplification.[27] But in double[14] blind multicentric study very high false positive results were obtained in many laboratories in developed countries leading to the recommendations that at present neither should the clinician initiate or discontinue anti-tuberculosis treatment, solely on the basis of result obtained in the PCR test.[28-29]
CONCLUSION
The statistical significance of Gastric Lavage AFB +ve is 70.3% of patients and its P value is significant over ESR test, TBIgG Test, ADA Test.
Therefore Gastric Lavage Test can be considered as one of the Diagnostic Test for suspected cases of Tuberculosis.
ACKNOWLEDGEMENTS
We sincerely thank the Dean Dr. SK Goel for giving permission to publish the data. We also thank the staff of pathology department Dr. (Mrs.) Prachi Bedekar, Mrs. Uma Clerk and staff of R. RI (H) Mumbai for helping to prepare the Manuscript. We acknowledge our thanks to our 2nd Year Pathology student Mr. L Rebello for his valuable help.
REFERENCES
1.Koch A. The global tuberculosis situation and the new control strategy of WHO. 1991; 72.
2.Fourle PB, et al. Procedure for developing a sample scoring method based on unsophisticated criteria for screening children for tuberculosis. Int J Tuberc Lung Dis 1998; 2 (2) : 116.
3.Gothi GD, et al. Tuberculosis in children in a slum community. Ind J Tuber 1997; 24 : 2.
4.WHO provisional guidelines for diagnosis and classification of EPI target diseases for primary health care, surveillance and special studies. EPI/GEN/88/4 Geneva. 1983.
5.Chakarabati AK, Ganoapathy KT, et al. Effect of nutritional status on delayed hypersensitivity due to tuebrculin test in the children of urbal slum community. Ind J Tub 1980; 27 (3) : 115.
6.Conte BA, Lafert EG. The role of topical anesthetic agent in modifying the bacteriologic data obtained by bronchoscopy. N Engl J Med 1962; 267 : 957.
7.Kenneely DJ, Lewis KPP, Barnes PJ. Yield of bronchoscopy for diagnosis of tuberculosis in patients with human immunodeficiency virus infection chest. 1992; 102 : 1040.
8.Fincher RMF. Clinical significance of extreme elevation of erythrocyte sedimentation rate. Arch Intern Med 1986; 146 : 1581J.
9.Tmette ME, Schmid A, Baum J. Use of erythrocyte sedimentation rate in chronically elderly patients with decline in health status. American J Med 1983; 80 : 844-8.
10.Kenney RA, Saunders AP, Cole A, et al. A comparison of erythrocyte sedimentation rate and serum c-Reactive protein concentration in elderly patients. Age Ageing 1985; 14 : 15-50.
11.Katz PR, Karuga J, Gutmen S, et al. A comparison between erythrocyte sedimentation rate selected acute phase proteins in the elderly. Am J Clin Path 1990; 94 : 637-40.
12.Youmans GP. Relationship between delayed hyeprsensitivity and CMI. Am Revw Resp Dis 1975; 111 : 373.
13.Dannenberger. Am Jr. Delayed type hypersensitivity and cell mediated immunity in the pathology of tuberculosis. Immunology Today 1991; 12 : 228.
14.Standford JL, Shield MJ, Rook GAW. How environmental mycobacterium may predetermine the protective efficacy of BCG Tubercle. 1981; 62 : 55.
15.Rook GAW, Bahr GM, Standford JL. The effect of two distinct forms of cell mediated response to mycobacterium on the protective efficacy of BCG Tubercle. 1981; 62 : 63.
16.National tuberculosis institute of Bangalore. Tuberculosis in a rural population of South India Bull Wld Hlth Org. 1974; 51 : 473.
17.Grzybowsky S. Cast of tuberculosis control. Tubercle 1987; 68 : 33.
18.Daniel TM, Debanne SM, von der Kung. Enzyme linked immunoabsorbent assay using mycobacterium tuberculosis. Antigen 5 and PPE for sero diagnosis of tuberculosis. Chest 1985; 88 : 388-92.
19.Rattan A, Shrinivas. Western Blot Analysis of immune response in pulmonary TB. Indian J Tuber 1991; 38 : 11-5.
20.Wikins EGL, Ivany IJ. Potential value of serology for diagnosis of extra pulmonary tuberculosis. Lancet 1990; 336 : 641-4.
21.Drowart A, Selleslaghs J, et al. The humoral immune response after BCG vaccination on immunoblotting study using purified antigens. Tubercle Lung Disease 1992; 63 : 137-40.
22.Von Vooren JP, et al. Antimycobacterial antibodies in pleural effusion. Chest 1990; 97 : 88-90.
23.Hurate T, Mizoghi K, Amanoh, et al. Antipurified protein derivative in tuberculosis pleural effusion.
24.Ribera E, et al. Activity of adenosine deaminase in CSF for diagnosis and follow up of tuberculosis meningitis in adults. J Infect Dis 1987; 155 : 603-7.
25.Ocora J. Seura KM Adenosine Deaminase activity pleural effusion. Chest 1983; 85 : 51-3.
26.Martinez JM. Ribera Adenosine Deaminase activity in tuberculosis pericarditis. Thorax 1986; 41 : 888-89.
27.Wilsom SM, Menerney R, Nye PM, et al. Progress towards a simplified polymerase chain reaction and application in diagnosis of tuberculosis. J Clinical Microbiology 1993; 31 : 776-82.
28.Grasset Jmauton Y. Is PCR a useful tool for the diagnosis of tuberculosis in 1995. Tubercle Lung Dis 1995; 76 : 183-4.
29.Noordhook GT, Kolk HJ, Bjune G, et al. Sensitivity and specificity of PCR for the detection of mycobacterium tuberculosis a blind comparison study among seven laboratories. J Clin Microbiology 1994; 32 : 277-84.
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