Analytical validation of hepatitis B core-related antigen (HBcrAg) using dried blood spots (DBS).

Limited access to nucleic acid testing (NAT) to quantify HBV DNA levels, an essential tool to determine anti-HBV treatment eligibility, represents a significant barrier to scale up HBV diagnostic services in resource-limited countries. Hepatitis B core-related antigen (HBcrAg) has the potential to become an affordable alternative because of its low cost (US$ <15/assay) and strong correlation with HBV DNA levels in treatment-naïve patients. However, the current assay requires plasma or serum. To further facilitate its application to decentralized settings, we developed and evaluated a standardized procedure to quantify HBcrAg using dried blood spots as a tool to diagnose HBV-infected people with high viraemia. We evaluated the following elution method optimized to quantify HBcrAg: suspension of a punched blood-soaked disc (11 mm) of Whatman 903 Protein Saver Card in 450 µL of PBS 0.05% Tween 20, followed by an incubation for 4 h at room temperature and a centrifugation at 10,000 g for 10 minutes. 150 µL of DBS eluate was used to quantify HBcrAg using chemiluminescent enzyme immunoassay (LUMIPULSE® G600II, Fujirebio). The limit of detection of dried blood spot HBcrAg in relation with HBV DNA levels was 19,115 IU/mL across the five major HBV genotypes (A/B/C/D/E). A strong linear correlation was confirmed between dried blood spot HBcrAg and HBV DNA levels (r = 0.94, p < 0.0001) in samples with high viral loads (range: 3.7-7.0 log IU/mL). The coefficient of variation ranged between 4.0-11.2% for repeatability and 3.9-12.2% for reproducibility. Analytical specificity was 100% (95% CI: 83.9-100%) in HBV-negative samples. Using our elution method, it may be possible to identify HBV-infected patients with high viraemia who need antiviral therapy using dried blood spot and HBcrAg. A large-scale clinical validation is warranted in resource-limited countries.

Biomarkers for the early stages of clinical development in Alzheimer's disease.

As the failure of several recent Phase III drug development programmes bears witness, the clinical development of "disease-modifying" drugs in Alzheimer's disease has been confronted with challenging methodological difficulties. Taking into account the financial stakes involved taking drug candidates to the Phase III stage of development, and the risk of investing time and resources fruitlessly in the evaluation of poor candidate drugs, the crucial decision remains whether to proceed from Phase II to Phase III (Go/Nogo). The aim of Phase II studies is to select a molecule likely to be effective in Phase III, but also to eliminate candidate-drugs with an inadequate effect. No consensus currently exists on the best possible design of Phase II studies to inform the Go/Nogo decision optimally. The challenges in choosing the best study design relate to the target population, the end-point criteria used, in particular the use of biomarkers, the experimental protocol, and the study duration. The objective of the Round Table (RT) was to gather the opinions of French experts from the academic, industrial, and regulatory world in order to arrive at a consensus recommendation for the best possible design to be used in Phase II studies in Alzheimer's disease.