External quality assessment to support the WHO ProSPeRo study for the evaluation of two dual HIV/syphilis point-of-care tests in seven countries.

BACKGROUND: Sexually transmitted infections (STIs) such as syphilis and HIV remain to be a significant public health issue worldwide. Dual rapid point-of-care tests (POCTs) have shown promise for detecting antibodies to HIV and syphilis but have not been fully evaluated in the field. Our study supported the WHO ProSPeRo study on Sexually Transmitted Infection Point-of-Care Testing (STI POCT) by providing external quality assessment (EQA) for HIV and syphilis testing in reference laboratories and their associated clinical sites in seven countries. METHODS: HIV/syphilis serum liquid and dried tube specimen (DTS) panels were prepared by CDC. Liquid panels were distributed to the reference laboratories for three rounds of testing using commercially and locally available laboratory-based serological tests. DTS panels were sent to the clinical testing sites for 8 rounds of POC testing using the Abbott SD BIOLINE HIV/Syphilis Duo test (hereafter referred to as SD BIOLINE) and the Chembio Dual Path Platform (DPP) HIV-Syphilis assay. EQA panels were tested at CDC using the Rapid Plasma Reagin (RPR) test and the Treponema pallidum Particle Agglutination assay (TP-PA) for syphilis antibodies. Genetic Systems HIV-1/HIV-2 Plus O EIA, Geenius HIV Supplemental Assay and the Oraquick Advance HIV test were used to detect HIV antibodies in the EQA panels. Results from the reference laboratories and POCT sites were compared to those obtained at the CDC and a percentage agreement was calculated. RESULTS: Qualitative RPR and TP-PA performed at the reference laboratories demonstrated 95.4-100% agreement with CDC results while quantitative RPR and TP-PA tests demonstrated 87.7% and 89.2% agreement, respectively. A 93.8% concordance rate was observed for qualitative HIV testing in laboratories. EQA testing at clinical sites using dual tests showed 98.7% and 99.1% agreement for detection of HIV antibodies and eight out of 10 sites had > 95.8% agreement for syphilis testing. However, two clinical sites showed only 65.0-66.7% agreement for SD BIOLINE and 84.0-86.7% for DPP, respectively, for syphilis testing. CONCLUSIONS: Overall, laboratories demonstrated high EQA performance in this study. Both HIV/syphilis POCTs gave expected results in the clinic-based evaluations using DTS. However, testing errors were identified in a few testing sites suggesting the necessity for continuous training and monitoring the quality of POC testing.

Molecular investigation of Treponema pallidum strains associated with ocular syphilis in the United States, 2016-2020.

Ocular syphilis is a serious complication of Treponema pallidum infection that can occur at any stage of syphilis and affect any eye structure. It remains unknown if certain T. pallidum strains are associated with ocular infections; therefore, we performed genotyping and whole genome sequencing (WGS) to characterize strains from patients with ocular syphilis. Seventy-five ocular or non-ocular specimens from 55 ocular syphilis patients in 14 states within the United States were collected between February 2016 and November 2020. Sufficient T. pallidum DNA was available from nine patients for genotyping and three for WGS. Genotyping was done using the augmented Centers for Disease Control and Prevention typing scheme, and WGS was performed on Illumina platforms. Multilocus sequence typing allelic profiles were predicted from whole genome sequence data. T. pallidum DNA was detected in various specimens from 17 (30.9%) of the 55 patients, and typing was done on samples from 9 patients. Four complete strain types (14d10/g, 14b9/g, 14d9/g, and 14e9/f) and five partial types were identified. WGS was successful on samples from three patients and all three strains belonged to the SS14 clade of T. pallidum. Our data reveal that multiple strain types are associated with ocular manifestations of syphilis. While genotyping and WGS were challenging due to low amounts of T. pallidum DNA in specimens, we successfully performed WGS on cerebrospinal fluid, vitreous fluid, and whole blood.IMPORTANCESyphilis is caused by the spirochete Treponema pallidum. Total syphilis rates have increased significantly over the past two decades in the United States, and the disease remains a public health concern. In addition, ocular syphilis cases has also been on the rise, coinciding with the overall increase in syphilis rates. We conducted a molecular investigation utilizing traditional genotyping and whole genome sequencing over a 5-year period to ascertain if specific T. pallidum strains are associated with ocular syphilis. Genotyping and phylogenetic analysis show that multiple T. pallidum strain types are associated with ocular syphilis in the United States.