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Abstract
Background
Current status of external quality assessment (EQA) of laboratory tests for syphilis in Korea was analyzed to find out the problems that should be improved in the future.
Methods
Based on the data from the external quality assessment program performed twice a year by the Immunoserology Subcommittee of the Korean Association of Quality Assurance for Clinical Laboratory from the year 2004 to 2006, discordance rates were analyzed according to the test method and commercial kit used.
Results
Among the laboratories participating in the EQA program for syphilis test, about 90% of them used non-treponemal tests and about 55% treponemal tests. The non-treponemal tests included RPR (rapid plasma reagin) and VDRL tests used in 88% (363/412) and 11% (45/412), respectively, of the laboratories. The discordance rates were 2.2% for RPR test and 3.6% for VDRL. For the treponemal tests, Treponema pallidum hemagglutination assay (TPHA) was used in 60-76% and Immunochromatography assay (ICA) in about 30% of the laboratories in 2006. A high discordance rate of over 10% was reported in both TPHA and in ICA methods, possibly due to a low titer (1:1 in VDRL) of EQA samples in 2005. Analysis of the accumulated data from year 2004 to 2006 showed that the discordance rates of TPHA, ICA, and FTA-ABS were 4.6%, 3.7%, and 2.7%, respectively.
Conclusions
For syphilis tests, RPR test, TPHA, and ICA are mainly used in Korea. A high discordance rate is still reported in TPHA and ICA, especially when testing samples with a low titer. Further analysis of data and education of laboratory personnel are needed for the improvement of the EQA program.
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 | Fig. 1.Distribution of the methods of non-treponemal tests used in Korea (2004-2006). Numbers of the participants who used each method were shown in each survey. Abbreviations: No., number; RPR, rapid plasma reagin; VDRL, Venereal Disease Research Laboratory; TIA, turbidoimmunoassay. |
 | Fig. 2.Distribution of the manufacturers of non-treponemal tests used in Korea (2004-2006). Accumulated numbers of the participants who used each method and kit during the 3 yrs of surveys (2004-2006) were shown. Abbreviations: No., number; RPR, rapid plasma reagin; VDRL, Venereal Disease Research Laboratory; TIA, turbidoimmunoassay; BD/BBL, Becton Dickinson. |
 | Fig. 3.Discordance rates of RPR test in Korea (2004-2006). Discordance rate was calculated as a number of participants with discordant results divided by a number of total participants. A discordant result was defined as a result different from the consensus (more than 80% of participants). Abbreviations: BD/BBL, Becton Dickinson; ASI, Arlington Scientific, Inc. |
 | Fig. 4.Distribution of the methods of treponemal tests used in Korea (2004-2006). Numbers of the participants who used each method were shown in each survey. Abbreviations: No., number; TPHA, Treponema pallidum hemag-glutination assay; ICA, immunochromatography assay; PA, particle agglutination; FTA-ABS, fluorescent treponemal antibody absorption test; EIA, enzyme immunoassay; TIA, turbidoimmunoassay. |
 | Fig. 5.Distribution of the manufacturers of TPHA, ICA, FTA-ABS, EIA, and TIA in Korea (2004-2006). Accumulated numbers of the participants who used each method and kit during the 3 yrs of surveys (2004-2006) were shown. Abbreviation: See Fig. 4. |
 | Fig. 6.Discordance rates of treponemal tests in Korea (2004-2006). Discordance rate was calculated as a number of participants with discordant results divided by a number of the total participants. The discordant result was defined as a result different from the consensus (more than 80% of participants). Abbreviations: TPHA, Treponema pallidum hemagglutination assay; ICA, immunochromatography assay; FTA-ABS, fluorescent treponemal antibody absorption test. |
 | Fig. 7.A number of participants with discordant results according to the RPR titer of quality assessment materials in CAP survey (2005-2006). Abbreviation: No., number. |
Table 1.
Comparison of discordance rates between the external quality assessment program of College of American Pathologists (2005-2006) and that of the Korean Association of Quality Assurance for Clinical Laboratory (2004-2006) for serologic syphilis tests
| CAP ('05-'06) | KAQACL ('04-'06) | |
|---|---|---|
| VDRL | 0.1% | 3.6% |
| RPR | 0.3% | 2.2% |
| TPHA/TP-PA/PK-TP | 0.1% | 4.2%∗ |
| FTA-ABS | 0.1% | 2.7% |
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