COMPARATIVE STUDY OF VDRL AND TPHA AND THEIR COMPLEMENTARY ROLES IN SERODIAGNOSIS OF SYPHILIS
JG SALUJA*, MS AJINKYA**, BHAVNA KHEMANI***
*Assoc. Prof. and HOD of Pathology; **Assoc. Prof. of Pathology; ***Chief Pathology Laboratory Technician, CMP Homoeopathic Medical College and Shri Mumbadevi Homoeopathic Hospital, Irla, Vileparle (W), Mumbai 400 056.
Western reports regarding comparison on VDRL and TPHA are few. VDRL and TPHA tests were compared in 200 sera obtained from various departments of Mumbadevi Homoeopathic Hospital - Vileparle. TPHA found to be 38% positive. VDRL 24.5% positive. Three patients were HIV positive. Out of three one was found to be TPHA positive (Biologic false positive). Infants born to mother having syphilis TPHA may be useful in concluding whether the infant should be treated or not.
Syphilis, a chronic systemic infection caused by "Treponema pallidum", is usually sexually transmitted and is characterised by episodes of active disease, interrupted by latency.
Syphilis serology is resorted to by clinicians for different purposes like antenatal care, to investigate cases of bad obstetric history and primary infertility and of course to confirm a suspected case of syphilis.
Among the serological tests for syphilis VDRL is the most inexpensive and commonly done test. In clinically unsuspected cases a reactive VDRL should always be checked with treponemal test like TPHA, FTA, ABS, TPI tests. TPHA test is routinely done in many laboratories in our country as a confirmatory test. Western reports regarding the comparison on VDRL and TPHA are few.[1-2]
Here in we report our experience as regard the results of VDRL and TPHA tests.
MATERIAL AND METHODS
Two hundred sera’s were collected from patients of different departments of Shri Mumbadevi Homoeopathic Hospital between a period from Jan. 1999 to December 2000 for screening of VDRL and TPHA test. The VDRL antigen and TPHA kit was supplied by Qualingens (Glaxo); RPR card test for VDRL and ELISA for TPHA test.
Based on clinical indication we divided patients in three groups as follows:
Group I Clinical suspicious/evidence of syphilis
Group II Clinical evidence of other sexually transmitted diseases (STDs)
Group III VDRL done on routine basis (Antenatal care clinic)
In Group I Clinical suspicious/evidence of syphilis
Total number of patients in this group was thirty five.
VDRL Fourteen (14) strongly +ve in titre 1:16 Seven(7) weakly +ve in titre 1:4
Seven (7) were -ve even after dilution
(Rule out Prozone Phenomenon)
TPHA test - Sixteen (16) were +ve in titre 1:250
In Group II Clinical evidence of other STDs.
Total number of patients in this group was ten (10).
VDRL test - Three (3) were weakly reactive in titre 1:8
TPHA test Eight (8) were +ve in titre 1:250
In Group III Routine screening VDRL during ANC.
One hundred fifty five (155) number of patients in these group were screened for VDRL test.
VDRL test Thirty five (35) were +ve in titre1:16 Five (5) were weakly +ve in titre 1:4
TPHA test Forty six (46) were +ve in titre 1:250 Four (4) were +ve in titre 1:125
One hundred (100) patients which were negative for VDRL were subjected to dilution (Prozone phenomenon) and we found twenty (20) patients to be positive for VDRL in titre 1:8. Whereas out of these twenty patients, only twelve (12) patients turned out to be TPHA positive in titre 1:80.
In this group of antenatal care, we found three (3) patients to be HIV positive by ELISA and confirmed positive by Western Blot Assay. All patients a detail history of major illness were ruled out except in 2% of antenatal care patients who had history of malarial fever, P/H of Rheumatoid factor (RA factor) positive in low titre 1:32.
Fifteen (15) patients were weak positive. These patients were subjected to TPHA test, and thirteen (13) were TPHA positive (1:125).
Group No. of Patients Indication of syphilis serology Positive No. VDRL % Weak No. Positive %. Positive No. TPHA %
35 Clinical suspicious 14 40% 07 20% II 10 Clinical evidence of other STDs - 0% 03 30% 08 80% III 155 Routine screening (ANC) 35 22.6% 05 3.2% 50 32.3%
Overall results of VDRL and TPHA
Total No. of patients VDRL No +ve % VDRL
weakly +ve % TPHA
+ve % 200 49 24.5% 15 7.5% 76 38%
Three patients who were HIV +ve, out of the three one was found to have TPHA +ve (may be false positive) and two (2) were VDRL positive in lower titre (1:4).
Although cost effectiveness of VDRL test makes it a common screening test for syphilis. We have seen from above study that there are many weak positive cases and cases showing Prozone phenomenon in VDRL tests. Hence to accurately diagnose and confirm syphilis it would be better to do TPHA along with VDRL in most of the cases.
Now a days with rising urban population makes leading life alone, and there is a high tendency for STD with irregular treatment and repeated exposure. This involves difficulty in reporting cases which are VDRL positive, than when a biological false positive, that which are really positive but in low titre. The biological false positive can fall into two main groups.[4-5]
(a)Acute biological false positive cases which can be due to viral, bacterial infection, vaccination and immunization, malarial parasite.
(b)Chronic biological false positive cases which are due to SLE, cardiovascular diseases, autoimmune disorders. 70% of them are women. The other group of weakly positive cases may be that the patient is suffering from syphilis either in 1st or 3rd stage of disease and those who have taken irregular or partial treatment. To differentiate them TPHA is very important since it is negative in biological false positive cases and positive in early 1st stage and in 3rd stage of syphilis and remain positive even after treatment. The instances where VDRL negative and TPHA positive, may be the fully treated patient and in case of non-venereal treponemal infection. Infant born to mother having syphilis and being treated during pregnancy also show variable status of VDRL. Again the TPHA may be useful in concluding whether the infant should be treated or not. If the infant is TPHA positive in early weeks of life a repeat TPHA after 1 month may illustrate positive status of infant. Moreover TPHA should be done in blood transfusion products as VDRL may be weak positive or may be prozone phenomenon and be falsely interpreted as negative.
In 1982, Barbara had recommended discarding VDRL test and depend on TPHA for serological diagnosis of syphilis. TPHA is found to be superior in sensitivity and specificity over VDRL as seen in our studies and is consistent with H. Young et al.
Thus both the tests have advantage in certain situations individually. But when performed dually on one sample can exactly give information, whether the patient is serologically reactive to syphilis and hence we suggest a dual tests by both method, for testing Group I i.e. those having strong clinical suspicion of syphilis and Group II i.e. those having other STD patients.
We are thankful to the Dean Dr. SK Goel for giving us permission to publish the data.
1Lesinkin J, Krach J, et al. Specificity, sensitivity and diagnostic value of TPHA test. Journal of Venereal diseases 1974; 50 : 334.
2Pukutt A, Pratt G. Syphilis screening in blood transfusion service, a report of four years experience with TPHA and subsequent development of a rapid "Spim" method. Journal of Clinical Pathology 1987; 40 : 1331-9.
3.Harison. Principles of internal medicine. 14th edition. Vol. 9 : 1029-30.
4.Harish BN, Rao RS, et al. Antiseptic comparative study of VDRL and TPHA. 1992; 89 (9) : 481-82.
5.Gradwohl’s Clinical Laboratory methods and diagnosis 8th edition. 1990; 2264-65.
6.Barbara JAT, Salkar R, Lalji F. TPHA compared with cardiolipin tests for serological detection of early primary syphilis. Journal of Clinical Pathology 1982; 35 : 1394-5.
7.Young H, et al. TPHA test as screening procedure for diagnosis of syphilis. Journal of Venereal diseases 1974; 50 : 341.