Passive Particle Agglutination Research Articles

Clinical Value of Different Test Methods in Diagnosing Mycoplasma pneumoniae Infection in Children.

This research aimed to investigate the diagnostic value of passive particle agglutination test, Mycoplasma pneumoniae (MP) culture, cold agglutination test (CAT), enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction-capillary electrophoresis fragment analysis (PCR-CEFA) for MP infection. Children with respiratory tract infections suspected to be MP infection were subjected to passive particle agglutination test, MP culture, CAT, ELISA, and PCR-CEFA. A total of 146 children (81 males, 65 females, mean age: 5.74 ± 3.32 years, and mean course of disease: 9.07 ± 5.18 days) met the inclusion criteria. The positivity rate of MP detection by MP culture was 69.18% (101/146). Using the MP culture method as the standard, higher sensitivity and positive predictive value were found in the PCR-CEFA compared with the other 3 methods. Appropriate methods are selected following the advantages and disadvantages of pathogen detection, and pediatric MP infection is analyzed by integrating various test results.

Comparison of serodiagnosis methods for community-acquired Mycoplasma pneumoniae respiratory tract infections in children.

This study aimed to evaluate the diagnostic value of chemiluminescence immunoassay (CLIA), passive particle agglutination (PPA), and indirect immunofluorescence assay (IFA) in detecting Mycoplasma pneumoniae infection in children. Serum samples from 165 children with acute community-acquired respiratory tract infections were examined using CLIA, PPA, and IFA, and consistency coefficient, specificity, and sensitivity were analyzed. Compared with the PPA (titer ≥ 1:160), the consistency coefficients of the immunoglobulin(Ig)M-CLIA, immunoglobulin(Ig)G-CLIA and IgM-IFA methods were 93.94%, 75.76%, and 83.64%, respectively. The positive likelihood ratio (PLR) and specificity of IgM-CLIA was 19.40 and 95.49%, respectively. The consistency coefficient of (IgM+IgG)-CLIA and PPA (titer ≥ 1:160) was 89.1%, and the sensitivity and negative predictive value of (IgM+IgG)-CLIA were 96.88% and 98.94%, respectively. CLIA MP-IgM has high concordance with PPA, and its specificity and sensitivity are higher than those of CLIA MP-IgG and IFA MP-IgM, suggesting its better diagnosis of early MP infection. The sensitivity and negative predictive value of CLIA MP (IgM+IgG) were higher than those of PPA or IFA, indicating that it should be considered as a priority in the diagnosis of MP infection.

British Columbia's Experience after Implementation of the Treponema pallidum Reverse Algorithm and PCR Detection, 2015 to 2020.

ABSTRACTBritish Columbia (BC) implemented the syphilis reverse screening algorithm and Treponema pallidum PCR testing in 2014. We summarize the performance characteristics of the algorithm, together with PCR direct detection, and report on syphilis cases identified from 2015 to 2020. Prior to 2015, samples for syphilis diagnosis were first screened by rapid plasma reagin (RPR). As of 2015, sera were screened by the Siemens Advia Centaur syphilis assay (enzyme immunoassay [EIA]). Positive and equivocal samples were reflex tested by a T. pallidum passive particle agglutination assay (TPPA) and RPR. We used T. pallidum DNA PCR on clinical samples and restriction fragment length polymorphism analysis to identify azithromycin resistance mutations. Case/epidemiological data were obtained from the BC surveillance system. Of 1,631,519 samples screened by the EIA, 72,492 (4.4%) were positive and 187 (<0.1%) were equivocal. Of EIA-positive/equivocal samples, 10.6% were false positive, and false positivity was higher at lower EIA indices. The reverse algorithm detected 4,693 late latent syphilis cases that likely would have been missed by RPR screening. PCR had a very high sensitivity of 100% versus 52.9% and 52.4% for dark-field (DF) and immunofluorescence (IF) microscopy, respectively. The azithromycin resistance mutation A2058G was identified in 96% of PCR-positive samples, and A2059G was identified in 4%. Annually, there were 944 to 1,467 syphilis cases, with 62% in men who reported male sexual partners. The reverse algorithm had a low false-positive rate and very few equivocal screening results but did identify previously undiagnosed late latent syphilis cases. PCR was more sensitive than both DF and IF microscopy for direct diagnosis and enabled monitoring for azithromycin resistance.IMPORTANCE In this study, we summarize the performance characteristics of the algorithm, together with PCR direct detection and epidemiological analysis, and report on syphilis cases identified from 2015 to 2020. This allowed us to paint a complete picture of the outcome of the utilization of the reverse algorithm for diagnosing syphilis cases. The study clearly showed that the reverse algorithm had a low false-positive rate and very few equivocal screening results but did identify previously undiagnosed late latent syphilis cases. PCR was more sensitive than both DF and IF microscopy for direct diagnosis and enabled monitoring for azithromycin resistance.

Clinical presentation and serological diagnosis of syphilis reinfection in men living with HIV: a retrospective cohort study

ObjectivesStudies on the characteristics of syphilis reinfection are scarce despite increasing numbers and proportions of cases. We aimed to gain insights into the clinical and serological presentation of reinfected men...

Laboratory Examination of Syphilis

Syphilis, is sexually transmitted disease caused by spirochete Treponema pallidum subsp.pallidum. It have many diverse clinical manifestations that occur in distinct stages. Early diagnosis and management are the main things to prevent transmission and complication. Direct test or morphological observation is the definitive diagnosis of syphilis. This can be done through animal inoculation test, dark field microscopy, direct fluorescence antibody (DFA), and nucleid acid amplification test (NAAT). While the indirect test is a nontreponemal serologic test consist of Wasserman test, venereal disease research laboratory (VDRL), toluidine red unheated serum test (TRUST), unheated serum reagin (USR), rapid plasma reagin (RPR) and treponemal serologic test, such as T. pallidum passive particle agglutination (TPPA), T. pallidum haemagglutination assay (TPHA), fluorescent treponemal antibody absorption (FTA-Abs), enzyme immunoassay (EIA) and rapid test. The algorithm of serologic test can be divided into traditional or reverse.

Laboratory Examination of Syphilis

Syphilis, is sexually transmitted disease caused by spirochete Treponema pallidum subsp.pallidum. It have many diverse clinical manifestations that occur in distinct stages. Early diagnosis and management are the main things to prevent transmission and complication. Direct test or morphological observation is the definitive diagnosis of syphilis. This can be done through animal inoculation test, dark field microscopy, direct fluorescence antibody (DFA), and nucleid acid amplification test (NAAT). While the indirect test is a nontreponemal serologic test consist of Wasserman test, venereal disease research laboratory (VDRL), toluidine red unheated serum test (TRUST), unheated serum reagin (USR), rapid plasma reagin (RPR) and treponemal serologic test, such as T. pallidum passive particle agglutination (TPPA), T. pallidum haemagglutination assay (TPHA), fluorescent treponemal antibody absorption (FTA-Abs), enzyme immunoassay (EIA) and rapid test. The algorithm of serologic test can be divided into traditional or reverse.

Who gets a laboratory positive diagnosis of Mycoplasma pneumoniae: A 10-year retrospective analysis

• Over 10-years, 278 patients were positive for Mycoplasma pneumoniae. • Median patient age was 40-years; 80% had abnormal chest radiology. Mortality was 1.3%. • There was poor correlation between PCR and serology positivity (29%). Mycoplasma pneumoniae ( M. pneumoniae ) is thought to cause up to a third of community acquired pneumonias (CAP), but may be undiagnosed due to limitations with current diagnostics, and untreated given the frequent use of B-lactams to which M. pneumoniae is not susceptible. We performed a ten-year retrospective analysis to identify the typical characteristics of a patient with a laboratory positive diagnosis of M. pneumoniae . Laboratory diagnosis of M. pneumoniae was performed using Polymerase Chain Reaction (PCR) and Serology (passive particle agglutination (PPA) and Enzyme-linked immunosorbent (EIA) assays). Data were collected on all patients tested for M. pneumoniae between 2009 and 2019. 19,090 PCR and 4530 serology samples were tested for M. pneumoniae with 278 positive results. The positive group had a median age of 40 years (interquartile range 30–41 years); Median C-reactive Protein (CRP) was 71 mg/L, White blood Cell Count (WBC) 7 × 10 9 . 80% had an abnormal Chest X-ray. Intensive Care Unit (ICU) admission occurred in 4.5%; 1.3% patients died. 29% of patients were positive on both serology and PCR testing platforms. The characteristics reported here could be used as guidance on who is treated for M. pneumoniae. We propose that testing for M. pneumoniae needs to be performed systematically in patients with CAP; and that targeted atypical pathogen cover should be considered in preference to B-lactam mono-therapy for all patients with these characteristics.

Diagnostic Value of Serum ELISA of Mycoplasma Pneumoniae IgM and IgG and Passive Particle Agglutination for Mycoplasma Pneumoniae Pneumonia in Children.

The study was aimed to compare ELISA results of Mycoplasma pneumoniae IgG (MP-IgG) and Mycoplasma pneumoniae IgM (MP-IgM) with the passive particle agglutination (PA) test, as well as to evaluate their application value in the diagnosis of Mycoplasma pneumoniae pneumonia (MPP) in children. Serum MP antibodies were detected by ELISA for MP-IgM, MP-IgG, and PA for 292 patients in the MPP group and 89 patients in NMP group. The PA results were used as reference standards. These patients were treated in the respiratory department of Children's Hospital Capital Institute of Pediatrics, China, from July to December, 2019. In the MPP group, the positive rate for MP-IgM was 75% higher than that of the PA titer (73.97%), Pearson's coefficient was 0.711, and the Kappa coefficient was 0.662, p < 0.01, suggesting that both the correlation and the consistency of the two methods were high. In the PA-negative group (< 1:160), 22.38% of patients were MP-IgM positive, indicating that the sensitivity to MP-IgM was higher compared to PA, when the disease duration was less than 7 days. The diagnostic value for MP-IgG was lower than that for MP-IgM, and the high positive rate of MP-IgG (48.31%) in the NMP group suggested a high background value of MP-IgG in children. Testing of paired serum obtained a more accurate diagnosis. At admission, 47.57% of patients with paired serum who were negative for MP-IgM, converted to a net positive after 4 - 6 days, except for one patient. In the paired serum, 57.8% of patients had a 4-fold increase of MP-IgG. MP-IgM was a sensitive indicator of MP infection in children with a high consistency and correlation with the reference positive standard of PA titer ≥ 1:160. For a more accurate diagnosis, testing of paired serum is still necessary, and a 4-fold increase in MP-IgG could be the supplementary diagnosis method.

Diagnostic value of quantitative MP-IgG for Mycoplasma pneumoniae pneumonia in adults

The passive particle agglutination (PA) test, once widely used for Mycoplasma pneumoniae (M. pneumoniae) antibody detection, has gradually been replaced by quantitative enzyme-linked immunosorbent assays (ELISA). However, the lack of diagnostic criteria for quantitative ELISA M. pneumoniae-IgG (MP-IgG) and the low positive rates of ELISA M. pneumoniae-IgM (MP-IgM) limit the diagnostic value of ELISA for M. pneumoniae infection in adults. Here, the diagnostic value of quantitative ELISA MP-IgG was evaluated in adults with Mycoplasma pneumoniae pneumonia (MPP). The serum M. pneumoniae antibodies were detected in 162 patients with MPP, 228 patients with community-acquired pneumonia (CAP) with non-Mycoplasma pneumoniae (NMP), and 162 healthy controls by ELISA, using the PA results as the reference standards. For the MP-IgM−/IgG+ subgroup, a single serum MP-IgG level of ≥92.67 RU/mL can be used as a reference criterion for the diagnosis of acute M. pneumoniae infection. At admission, for patients with CAP, the sensitivity and specificity of ELISA MP-IgM positivity for MPP were 18.51% and 99.56%, respectively. MP-IgM positivity combined with MP-IgG ≥ 92.67 RU/mL increased the sensitivity to 40.12% and decreased the specificity to 94.29%. For paired serum samples obtained within seven days, an ELISA MP-IgG concentration change of ≥1.48-fold and MP-IgG ≥ 92.67 RU/mL on day 7 were used as the diagnostic criteria for M. pneumoniae infection. Accordingly, the combination of qualitative MP-IgM detection and quantitative MP-IgG detection by ELISA is valuable for acute MPP diagnosis in adults.

Dual screen and confirm rapid test does not reduce overtreatment of syphilis in pregnant women living in a non-venereal treponematoses endemic region: a field evaluation among antenatal care attendees in Burkina Faso

ObjectivesIn resource-limited settings, screening pregnant women for syphilis using rapid diagnostic tests (RDTs) is a key tool in the prevention of congenital syphilis. However, most syphilis RDTs detect only treponemal...

Performance of novel infection phase-dependent antigens in syphilis serodiagnosis and treatment efficacy determination

ObjectiveThe objective of this study was to screen new antigens for syphilis serodiagnosis. MethodsFirst, we determined whether the Treponema pallidum proteins Tp0971, Tp0768 and Tp0462 were infection phase-dependent antigens by observing serum reactivity differences in New Zealand rabbits infected with activated or inactivated T. pallidum. A non-infection phase-dependent antigen, the Tp92 membrane protein, was used as the negative control. Next, Tp0971-, Tp0768- and Tp0462-based ELISA was performed on 2138 human serum samples and compared with the T. pallidum passive particle agglutination assay (TPPA) and LiZhu™ Tp-ELISA. In addition, another 60 paired serum samples from patients at follow-up were analysed to evaluate the relationships between titre changes and differences in the A450 nm values of the Tp0971, Tp0768, Tp0462 and Tp92 antibodies measured by ELISA. ResultsCompared with Tp92 (negative control), Tp0971, Tp0768 and Tp0462 were determined to be infection phase-dependent antigens. Compared with those of the TPPA, the sensitivities of Tp0971-, Tp0768- and Tp0462-based ELISA were 96.4%, 96.9% and 93.0%, respectively, and the specificities were 97.7%, 95.4% and 98.9%, respectively, resulting in consistencies of 97.1%, 96.2% and 95.9%, respectively. Compared with those of the LiZhu™ Tp-ELISA, the consistencies of Tp0971-, Tp0768- and Tp0462-based ELISA were 95.1%, 94.2% and 94.0%, respectively, with kappa values of 0.902, 0.884 and 0.880, respectively. Tp0971, Tp0768 and Tp0462 demonstrated high sensitivities and specificities, as well as high conformity to the TPPA and LiZhu™ Tp-ELISA. Moreover, a significantly positive Spearman rank correlation coefficient (0.82,*P < 0.05) was found between the difference in the A450 nm values of the Tp0971 antibody and the RPR titre change. ConclusionThe infection phase-dependent antigens Tp0971, Tp0768 and Tp0462 are promising for syphilis diagnosis, and Tp0971 may be utilized to monitor curative effects during syphilis treatment.

Simultaneous detection of Mycoplasma pneumoniae IgG and IgM using dual-label time resolved fluoroimmunoassay

Anti-Mycoplasma pneumoniae (MP) IgM and IgG are useful serological markers for detection of MP infection. In this study, a simultaneous quantification of MP IgM and IgG was performed by time-resolved fluoroimmunoassay (TRFIA). The europium-labeled anti-human IgM and samarium-labeled anti-human IgG were used as tracers, and MP IgM and IgG were recognized in serum samples. After dissociating europium and samarium ions from the immune complex, their fluorescence intensity was recorded and used to calculate the concentrations. The linear range and sensitivity of detection were 2–5500 BU/mL and 0.5 BU/mL for IgM, and 1.5–1500 BU/mL and 0.2 BU/mL for IgG, respectively. The intra- and inter-assay coefficients of variation were 5.14% and 8.41% for IgM, and 5.44% and 8.76% for IgG, respectively. The recovery rate was 94.9–106.8% for IgM and 96.1–109.4% for IgG. The correlation rates of serum detection for 38 respiratory infected patients between dual-label TRFIA and ELISA were 0.9294 and 0.9366 for IgM and IgG, respectively. The coincidence rate between passive particle agglutination and TRFIA is 93.3%. Dual-label TRFIA is a sensitive and reliable technique for measuring MP IgM and IgG levels and could be useful for the early diagnosis of MP infection.

A comparison study between GeXP-based multiplex-PCR and serology assay for Mycoplasma pneumoniae detection in children with community acquired pneumonia

BackgroundDiagnosis of community-acquired pneumonia (CAP) caused by Mycoplasma pneumoniae (Mp) in children has been hampered by difficulty in obtaining convalescent serum and time constraints. In this study, the two diagnostic assays that targeted respectively on Mp-antibody and Mp-DNA were retrospectively investigated.MethodsA total of 3146 children were clinically diagnosed to have CAP and were confirmed by chest X-ray during March 2015 to February 2016 in Children’s hospital of Hebei Province (China). Both of the sera and sputum samples were collected in 24 h after their admission. The Mp-antibody was examined by the passive particle agglutination assay and a fourfold or greater increase of antibody titers of paired sera or≧1:160 titer of single serum was set as the serology positive. Mp-DNA in the sputum samples was tested by a multiplex-PCR method named GeXP assay (multiplex PCR combined with automated capillary electrophoresis). In order to eliminate the false positive results caused by the asymptomatic carriage after infected by M. pneumoniae, the inconsistent samples were tested by the real-time isothermal transcription-mediated RNA amplification assay (SAT).ResultsThe inter-rated agreement test was performed in 3146 CAP patients, with a highest kappa value in the school-age children as 0.783. There were 6.29% (198/3146) cases showed inconsistent results determined by GeXP and serology assay. All of the 19 GeXP(+)/Serology (−) samples and a randomly chosen 27 from 179 GeXP(−)/Serology (+) samples were tested by SAT assay, and a 97.8% diagnosis agreement was observed between SAT and GeXP assay, but not with the serology assay. In addition, patients who were detected only by serology or only by multiplex-PCR were significantly younger than those with both methods positive (3.0 and 1.5 years vs. 5.0 years, p < 0.01). The Viral-Mp coinfection accounted for 37.0% (97/262), which was more common in winter and spring (p < 0.05) and in the infantile group (p < 0.01), compared to the pure Mp positive ones.ConclusionIn some children CAP cases, the Mp laboratory diagnosis was inconsistent between serology and multiplex-PCR assay. Verified by the SAT assay, the GeXP showed a more sensitive and reliable performance compared with the serology assay. Furthermore, employing the multiplex-PCR could provide more information on the associated pathogens for clinical assessment of CAP.

Laboratory evaluation of the Chembio Dual Path Platform HIV-Syphilis Assay.

BackgroundUse of rapid diagnostic tests for HIV and syphilis has increased remarkably in the last decade. As new rapid diagnostic tests become available, there is a continuous need to assess their performance and operational characteristics prior to use in clinical settings.ObjectivesIn this study, we evaluated the performance of the Chembio Dual Path Platform (DPP®) HIV–Syphilis Assay to accurately diagnose HIV, syphilis, and HIV/syphilis co-infection.MethodIn 2013, 990 serum samples from the Georgia Public Health Laboratory in Atlanta, Georgia, United States were characterised for HIV and syphilis and used to evaluate the platform. HIV reference testing combined third-generation Enzyme Immunoassay and Western Blot, whereas reference testing for syphilis was conducted by the Treponema pallidum passive particle agglutination method and the TrepSure assay. We assessed the sensitivity and specificity of the DPP assay on this panel by comparing results with the HIV and syphilis reference testing algorithms.ResultsFor HIV, sensitivity was 99.8% and specificity was 98.4%; for syphilis, sensitivity was 98.8% and specificity was 99.4%. Of the 348 co-infected sera, 344 (98.9%) were detected accurately by the DPP assay, but 11 specimens had false-positive results (9 HIV and 2 syphilis) due to weak reactivity.ConclusionIn this evaluation, the Chembio DPP HIV–Syphilis Assay had high sensitivity and specificity for detecting both HIV and treponemal antibodies. Our results indicate that this assay could have a significant impact on the simultaneous screening of HIV and syphilis using a single test device for high-risk populations or pregnant women needing timely care and treatment.

The Diagnostic Value and Performance Evaluation of Five Serological Tests for the Detection ofTreponema pallidum

Syphilis is caused by the bacterium Treponema pallidum (TP). The aim of this study was to establish a clinical approach for serodiagnosis of syphilis by evaluating the performance and diagnostic value of five serological tests for the detection of TP. Five tests were used to test the serum from syphilis patients and control patients, namely rapid plasma reagin (RPR) test, toluidine red unheated serum test (TRUST), TP passive particle agglutination assay (TPPA), TP-specific enzyme-linked immunosorbent assay (TP-ELISA), and TP-specific chemiluminescent immunoassay (TP-CMIA). The sensitivity and diagnostic efficiency of TPPA (96.25%/98.38%), TP-ELISA (100%/95.41%), and TP-CMIA (100%/94.86%) were significantly higher than that of RPR (73.13%/86.22%) and TRUST (73.75%/86.49%) (P < 0.05). The minimum detectable concentrations for the five tests were 30 mIU/ml, 20 mIU/ml, 15 mIU/ml, 150 mIU/ml, and 150 mIU/ml, respectively. According to receiver operating characteristic (ROC) curve, the optimal cut-off values for syphilis diagnosis by TP-CMIA and TP-ELISA were 2.2 and 2.0 S/CO (where S/CO = Sample/calibrator cut off), and the area under the ROC curve (AUC) were 0.998 for TP-CMIA and 0.999 for TP-ELISA. The titers/positive rates for RPR and TRUST dropped from 1:4 (100%) to 1:1 (23.3%) (both P < 0.05) after treatment. However, there were no significant differences when we compared the positive rate of syphilis patients before and after treatment by TPPA, TP-ELISA, and TP-CMIA. Treponemal tests, such as TPPA, TP-ELISA, and TP-CMIA, are recommended for clinical routine screening of syphilis. However, nontreponemal tests, for example, RPR and TRUST, perform better in therapy response assessment. Serological test should be tailored to respective facilities and clinical demands.

Serologic Testing for Syphilis in the United States: A Cost-Effectiveness Analysis of Two Screening Algorithms

The introduction of automated treponemal enzyme immunoassays and chemiluminescence assays (EIA/CA) tests has led some laboratories in the United States to use new syphilis screening algorithms that start with a treponemal test. We compared the economic and health outcomes of this new algorithm with the standard algorithm from the perspective of the United States health system. We used a cohort decision analysis to estimate the expected costs and effects (including follow-ups and overtreatment) of the 2 algorithms from a health-care system perspective. In the standard algorithm, rapid plasma reagin (RPR) is followed (if reactive) by EIA/CA (Nontreponemal-First). In the new algorithm, EIA/CA is followed (if reactive) by RPR. If the RPR is negative, Treponema pallidum passive particle agglutination assay (TP-PA) test is used (Treponemal-First). For a cohort of 200,000 individuals (1000 current infections and 10,000 previous infections), the net costs were $1.6 m (Treponemal-First) and $1.4 m (Nontreponemal-First). The Treponemal-First option treated 118 more cases (986 vs. 868) but resulted in a substantially higher number of follow-ups (11,450 vs. 3756) and overtreatment (964 vs. 38). Treating the additional 118 cases might prevent 1 case of tertiary syphilis. The estimated cost-effectiveness ratios were $1671 (Treponemal-First) and $1621 (Nontreponemal-First) per case treated. The overtreatment was a function of the specificity of the EIA/CA and the lack of independence of EIA/CA and TP-PA. The Treponemal-First option costs slightly more and results in more unnecessary treatment.

Evaluation of Three Serological Tests Manufactured in Belarus for the Diagnosis of Syphilis

The performance of three serological tests manufactured in Belarus for the diagnosis of syphilis, i.e. a microprecipitation reaction (MPR) and two enzyme-linked immunosorbent assays (ELISAs) were compared with internationally recognized assays, namely the rapid plasma reagin test and the Treponema pallidum passive particle agglutination assay (TPPA). Sera from 392 consecutive patients attending Brest (Belarus) regional dermatovenereological dispensaries were tested. The sensitivity of the MPR test was low (77.3%) compared with the rapid plasma reagin test, while the specificity was high (100%). In contrast, both Belarusian ELISAs performed well when compared with the TPPA (sensitivities of 99.2% and 100%, specificities of 98.7% and 99.0%, respectively). There is a clear need to improve the sensitivity of the existing Belarusian MPR test or to use a more sensitive screening test in order to improve diagnosis of the disease in Belarus.

An immunofiltration device for the simultaneous detection of non-treponemal and treponemal antibodies in patients with syphilis

ObjectiveThe development of a rapid immunofiltration (flow-through) test for the simultaneous detection of non-treponemal and treponemal antibodies in the serum of patients with syphilis.MethodsThe assay is rapid, inexpensive, and requires...

Prevalence and correlates of HIV and syphilis infections among men who have sex with men in seven provinces in China with historically low HIV prevalence.

To assess HIV and syphilis infection among men who have sex with men (MSM) in Chinese regions with historically low HIV prevalence. A cross-sectional survey was conducted in 20 cities or districts across 4 provinces, 2 autonomous regions, and a municipality. Socioeconomic/behavioral risk factors were measured. Blood samples were tested for HIV via enzyme-linked immunosorbent assay and Western blot confirmation and syphilis via rapid plasma reagin and passive particle agglutination test for detection of Treponema pallidum Antibodies. Of 4983 MSM participants, 2.9% were HIV infected (range: 0%-15.1%) and 9.8% were syphilis infected (1.3%-29.3%). Syphilis infection was associated with older age [adjusted odds ratio (AOR) = 2.9; 95% confidence interval (CI): 2.0 to 4.3], not being married or cohabiting (AOR = 0.7; 95% CI: 0.5-0.9), less education (AOR = 1.3; 95% CI: 1.0 to 1.7), inconsistent condom use during anal sex with men (AOR = 1.4; 95% CI: 1.0 to 1.8), and living in inner Mongolia (AOR = 23.9; 95% CI: 9.7 to 58.6), Jilin (AOR = 7.9; 95% CI: 3.4 to 18.3), Heilongjiang (AOR = 7.1; 95% CI: 3.1 to 16.6), Liaoning (AOR = 6.1; 95% CI: 2.6 to 14.2), or Chongqing (AOR = 5.9; 95% CI: 2.5 to 13.9). HIV infection was associated with older age (AOR = 3.7; 95% CI: 2.0 to 6.7), less education (AOR = 2.9; 95% CI: 1.8 to 4.7), inconsistent condom use during anal sex with men (AOR = 1.9; 95% CI: 1.2 to 3.2), syphilis infection (AOR = 2.1; 95% CI: 1.3 to 3.4), and living either in Liaoning (AOR = 8.2; 95% CI: 1.1 to 61.4) or Chongqing (AOR = 57.2; 95% CI: 7.9 to 414.4). HIV and syphilis have reached alarming rates in China's MSM population, thus, appropriate responses are urgently needed.

Evaluation of two human plasma pools as candidate international standard preparations for syphilitic antibodies

A collaborative study was designed to asses two freeze-dried human plasma preparations containing anti- Treponema pallidum antibodies, 05/132 and 05/122, for their suitability as international reference reagents for syphilis serology. Both preparations are intended as replacements of the first international standard (IS) for syphilitic serum antibodies (HS). Samples were tested by eight laboratories using the T. pallidum passive particle agglutination assay (TPPA), the venereal disease research laboratory test (VDRL) and the rapid plasma reagin test (RPR). In addition a range of immunoassays was also used. The outcome of the collaborative study revealed that candidate standard 05/132 contains T. pallidum-specific IgG and IgM and is reactive in VDRL or RPR, and that 05/122 contains T. pallidum-specific IgG but is not reactive in either the VDRL or RPR test. Both 05/132 and 05/122 are reactive in the TPPA. On the basis of these results the Expert Committee on Biological Standardization of the World Health Organization designated 05/132 as the 1st IS for human syphilitic plasma IgG and IgM with a unitage of 3 IU per ampoule relative to HS and 05/122 as the 1st IS for human syphilitic plasma IgG with a unitage of 300 mIU per ampoule relative to 05/132.