Diagnostic value of Treponema pallidum PCR test in real practice.

BACKGROUND: Syphilis is a sexually transmitted infection (STI) caused by the pathogen Treponema pallidum. Its incidence is increasing in our country, especially among men who have sex with men (MSM). Serological tests are still the most widely used technique for diagnosis. The need for an early diagnosis has prompted the introduction of fast techniques, such as Treponema pallidum detection by polymerase chain reaction (PCR) on mucocutaneous samples. The objective of this work is to analyse the sensitivity of this technique in a series of patients diagnosed with syphilis at our centre. METHODS: Retrospective review of all cases diagnosed with syphilis at our centre between May 2017 and May 2021. RESULTS: A total of 203 cases of syphilis were diagnosed with serologic tests: 33% were primary syphilis and 53.1% secondary syphilis. PCR for Treponema pallidum was performed in 117 (57,6%) cases. The sensitivity was highest (95,2%) when performed on samples from mucocutaneous ulcers in primary syphilis. This value decreased to 69,4% in secondary syphilis, although there were variations between the types of samples. CONCLUSIONS: The PCR test has a high diagnostic value when performed on ulcer exudates in patients with primary syphilis. Its most relevant advantages in clinical practice are the possibility of an early diagnosis before serological tests during the window period, the ability to confirm reinfections in patients with persistent positivity of reaginic antibodies and a history of treated syphilis. Nevertheless, given that a negative PCR test may not rule out infection by Treponema pallidum, serologic tests are still necessary for everyday practice.

"The effectiveness of rapid antigen test-based for SARS-CoV-2 detection in nursing homes in Valencia, Spain".

The usefulness of the PANBIO ™ COVID-19 Ag rapid test for SARS-CoV-2 infection detection has not been widely studied, especially in specific population groups such as the elderly who are institutionalized. Rapid diagnostic tests have the potential to benefit testing strategies, as they have short turnaround times, they are cheap, simple to perform and can be used in decentralized testing. The objective of this study is to show the performance of the PANBIO™ COVID-19 Ag Rapid test device conducted at geriatric institutions and to compare results to those obtained from RT-PCR. A total of 448 individuals were enrolled in the study, including both residents and employees. Nasopharyngeal swabs were collected for both PANBIO™ COVID-19 Ag Rapid test and RT-PCR testing. All the samples were analyzed by specialized microbiologists. A total of 117 out of 448 individuals (26%) tested positive by RT-PCR, of whom 99 (85%) returned positive Antigen test results. There were 18 Antigen negative cases with positive RT-PCR results. Accordingly, concordance between RT-PCR and Antigen test results was acceptable (K index, 0.89; 95% IC 0.8455-0.9345). Overall sensitivity and specificity of Antigen test was 85% and 100%, respectively. When defining RT-PCR CT positivity on a cut-off value of 35, LFA sensitivity was 90%. In case a cut-off value of 30 was used, LFA would increase up to 99%. In this real-life evaluation of the PANBIO™ COVID-Ag rapid test, the assay reliably identified SARS-CoV-2 infected individuals with low CT-values by RT-PCR. False negative results were observed only at high CT-values, meaning low viral loads in nasopharyngeal samples.

Hepatitis C virus core antigen in the management of patients treated with new direct-acting antivirals.

We evaluated the utility of Architect core antigen assay® Abbott Diagnostics (HCVAg) for monitoring patients with HCV infection and compared to HCV-RNA quantification (Cobas Ampliprep TaqMan-Roche Diagnostics). Samples from 262 patients were studied. Mean baseline HCV RNA and HCVAg levels were similar for responders (6.2 log IU/mL and 3.4 log fmol/L) and non-responders (6.1 log IU/mL and 3.2 log fmol/L), respectively. Only 10 patients failed to achieve SVR12 and all were detected by both assays. To evaluate HCVAg quantification as a tool for the detection of failure to DAAs, we performed a retrospective study of 132 non-responder patients. Mean HCV RNA and HCVAg levels at the time of detection of therapeutic failure were 5.88±0.97 log IU/mL and 3.19±0.79 log fmol/L, respectively. HCVAg (>3 fmol/L) was detected in 130/132 patients (98.5%). HCVAg assay was useful for patient selection and for evaluating virological response to DAAs in the real world.