Usefulness of dried blood spot samples for monitoring hepatitis C treatment outcome and reinfection among people who inject drugs in a test‐and‐treat program

Abstract

Dried blood spots (DBS) are a reliable tool to diagnose viremic hepatitis C virus (HCV) infection. We evaluated the clinical performance of a DBS‐based molecular assay for the assessment of cure and reinfection after on‐site treatment at a harm reduction center (HRC). Genotyping from DBS samples was also assessed to discriminate reinfection from treatment failure. People who inject drugs (PWID) from an ongoing test‐and‐treat pilot at the largest HRC in Barcelona were included in the study. HCV‐RNA detection from DBS collected after treatment (with follow‐up at 12, 36, and 60 weeks) was compared with a molecular point‐of‐care test using finger‐stick blood (GeneXpert). Baseline and follow‐up DBS samples were genotyped by NS5B sequencing or commercial real‐time PCR. Among treated patients, 193 follow‐up DBS samples were tested. The DBS‐based assay showed 100% specificity (129/129), and sensitivity ranged from 84.4% to 96.1% according to different viral load cut‐offs (from detectable to 3000 IU/mL). Sensitivity as test of cure (follow‐up 12) ranged from 85.1% to 97.4%. Among the 64 patients with recurrent viremia, 10.9% had low viral loads (≤1000 IU/mL); HCV genotyping allowed us to classify 73.5% of viremic cases either as reinfection or as treatment failure. DBS samples are useful to assess cure and differentiate reinfection from relapse after HCV antiviral treatment in the real world, facilitating decentralization of treatment and posttreatment follow‐up in PWID. However, a fraction of patients presented with low viral loads, limiting viremia detection and genotyping in DBS and, therefore, repeat testing is recommended.

Identification of Benzodiazepine Use Based on Dried Blood Stains Analysis

“…Our concern is that there is no published literature regarding the analysis of blood stains on cotton fabric. Previous research related to DBS analysis is focused on the identification of drugs using cards for blood spots [ 22 , 25 , 29 , 30 , 31 ]. However, in pharmacology and toxicology, the study of DBS-MS on cotton fabric is of greater interest and more useful than by cards.…”

“…First of all, this method is quite simple, quick and, of course, is a minimally invasive technique that minimizes the risk of infection associated with the handling of the samples. Besides, it is a dry matrix and therefore the absence of fluids promotes the inactivation of pathogens, including HIV and hepatitis virus [ 31 , 32 ]. Furthermore, this method allows us to know in real time the amount of a particular drug in the blood, reducing the error that occurs, for example, with hair samples.…”