Studies on the rapid plasma reagin card test for the diagnosis of syphilis and its evaluation
[영문]In spite of the fact that many investigators have strived for an effective control of syphilis, it remains as a major and presently increasing public health problem.
The importance of the serologic tests for the diagnosis of syphilis is reflected in the fact that syphilis may simulate many other diseases thus rendering an accurate diagnosis difficult on the basis of clinical signs and symptoms alone.
Since Wassermann et al.(1906) developed the complement fixation reaction for the diagnosis of syphilis, many investigators have continued to search for a simple and accurate testing method. Many kinds of serological tests have been developed and reported by the stead efforts of many investigators. Nevertheless, most of these tests are so complex as to be restricted to routine serologic laboratories.
Portnoy et al.(1959) reported the Rapid Plasma Reagin(RPR) test for syphilis which is more rapid, economical and simple. But still this test has many disadvantages as a rapid performing field and office procedure, because it requires the usual laboratory equipment such as a centrifuge, a rotating machine, a
To substitute for these disadvantages of the RPR test, in 1962, Portnoy et al. developed the Rapid Plasma Reagin(RPR) card test for syphilis, which has the following advantages: a) Simplicity and rapidity of performance, b) Requires no laboratory equipment, c) Stable antigen suspension, d) Adequate sensitivity and
This RPR card test can be used as a rapidly performing screening test in field investigation, outpatient clinics, small laboratories and hospitals doing limited syphilis serology, and for predonors in blood banks. Private clinics which have
limited laboratory equipment and techniques for syphilis serology can also use this RPR card test as a tool in the rapid diagnosis of syphilis.
It was thought that this RPR card test is a useful tool in Korea for private physicians and as a mass survey for syphilis diagnosis. Portnoy patented the reagents needed for performing the RPR card test. Therefore, the author developed newly the reagents, and according to Portnoy's method evaluated the sensitivity and the specificity of the newly developed RPR card test compared with the VDRL, the Kolmer CF, and the RPCF tests.
On the other hand, the information on syphilis reported up to now in Korea has dealt mostly with prostitutes. In order to present one aspect of syphilis prevalence and to actually utilize this simple and rapid RPR card test in a field survey in Korea, the prevalence of syphilis infections among the members of the
Korean Service Corps was analyzed.
Materials and Methods
A. Rapid Plasma Reagin Card Test
1. Preparation of antigen solution
a. Prepare antigen emulsion to be used for VDRL tests.
b. Centrifuge measured volume of the antigen emulsion for 15 minutes at 2,000g at room temperature.
c. Without disturbing the sediment, decant the supernatant fluid by inverting the tube.
d. Resuspend the sediment with an equal volume of resuspending solution to that of the centrifuged antigen emulsion. This solution is used for the antigen suspension of the RPR card test.
2. Plasma and serum collection
The plasma and sera were collected from the total 3,142 cases of four testing groups and tested; syphilis suspected cases, 521, healthy young men, 611m, and the members of the Korean Service Corps, 2,010.
The plasma was collected by using the plasma collection slide which is made from a plastic-coated card board with a keyholeshaped depression of 2×4cm in the center of the board. The depressed area is coated with an anticoagulant and a reagent to aggregated blood corpuscles. By the used of this plasma collection slide, the plasma can be obtained within 1∼2 minutes from 3∼4 drops of blood.
The sera were collected in the usual manner. Blood was collected in a clean dry test tube, and allowed to clot, and serum was separated by centrifugation.
3. Test Methods.
The RPR card test was performed on all the specimens as follows: Using the capillary tube with a rubber bulb, remove 0.03ml. of plasma from the plasma collection slide, and put it on the diagnostic card. Add one drop of antigen suspension and mix gently but completely, using a clean toothpick. Shake by tilting
the diagnostic card to and fro for 4 minutes. Read macroscopically and report as "reactive" specimens showing characteristic clumping; report as "nonreactive" specimens not clumping.
The VDRL slide flocculation test was carried out on all the specimens by the method described in the manual, Laboratory procedures for modern syphilis serology.
The Kolmer CF test was carried out on the specimens predetermined reactive by one or both the RPR card and the VDRL test, according to the method described in the Applied laboratory technic.
The RPCF test was performed on the specimens predetermined reactive by one or both the RPR card and the VDRL test, utilizing one-fifth volume Kolmer CF method recommended by Cannefax and Garson. B. Evaluation of the RPR card test for syphilis
screening in a field survey.
2,010 Korea, Service Corps men were examined by the RPR card test compared with the VDRL, the Kolmer CF, and the RPCF tests. the reactive specimens by one or both the RPR card and the VDRL test were retested by the Kolmer CF and the RPCF tests.
Results and Summary
Of 3,142 cased tested by th RPR card and the VDRL test, 242(7.7 per cent) were reactive in both tests and 2,726(86.8 per cent) were nonreactive in both tests. Agreement, reactive and nonreactive, between the RPR card and the VDRL test results
was 94.5 percent. 242(82.0 per cent) of the 295 reactives in the RPR card test were reactive in the VDRL test, and 2,726(95.7 per cent) of the 2,847 nonreactive in the RPR card test showed nonreactive VDRL tests.
The sensitivity and specificity of the RPR card and the VDRL tests were compared by retesting the 245 cases by the RPCF test, which were reactive by one or both the RPR card and the VDRL test. Compared with the agreement between the VDRL and the RPCF tests, the better correlations of the results of the RPR card and the RPCF tests were observed.
Among 2,010, 245(12.0 per cent) reactive by one or both the RPR card and the VDRL test were retested by the RPCF test. Of 245(12.0 per cent), 116(5.7 per cent) were reactive in the RPCF test. 145(7.1 per cent) of 2,010, which were reactive by the
RPR card test, were retested by the RPCF test, and 109(5.4 per cent) of 145 were reactive in the RPCF test. 222(10.9 per cent) of 2,010, which wrer reactive in the VDRL test, were retested by the RPCF test and 108(5.3 per cent) of 222(10.9 percent) were reactive in the RPCF test.
The biologtical false positive rates of the RPR card and the VDRL tests based on the reactivity of the RPCF test showed 1.7 per cent in the RPR card test and 5.6 per cent in the VDRL test. From the foregoing data, the sensitivity of the RPR card test appears to be similar to that of the VDRL test, and the RPR card test indicates higher specificity than that of the VDRL test. The RPR card test might be a valuable screening test for the diagnosing of syphilis.
In a field application of the RPR card test, 2010 of the Korean Service Corps were examined and the VDRL, the Kolmer CF, and the RPCF tests were compared. 7.1 per cent of 2,010 cases were reactive in the RPR card test and 10.9 per cent were reactive in the VDRL test.
The reactive specimens by one or both the RPR card and the VDRL tests were retested by the Komer CF and the RPC tests. 6.3 per cent of 2,010 were reactive in the Kolmer CF test and 5.7 per cent in the RPCF test.