Methodology of community-based venous blood specimen collection for the harmonized diagnostic assessment of dementia for the Longitudinal Aging Study in India (LASI-DAD): Wave 2.

The prevalence of dementia is on the rise, with 60% of dementia cases existing in low- and middle-income countries. In India, the prevalence was reported to be 7.4%. Since the pathophysiology of dementia is multifactorial, the Harmonized Longitudinal Aging Study in India for the Diagnostic Assessment of Dementia (LASI-DAD) collected data to capture multiple domains, including venous blood specimens (VBS). VBS collection and assays help ascertain the overall health status of an individual, understand disease pathogenesis, and diagnose diseases. In community settings, blood assays also help identify disease trends. However, community VBS collections can often be challenging. Sample quality can be impaired due to individual, environmental, geographical, and pre-analytical processing factors. Therefore, standardization of the process is imperative to ensure biomarker data of high accuracy. LASI-DAD developed a systematic sample collection, shipment, processing, and storage protocol. Multiple checkpoints were in place to monitor sample quality in real time. A phlebotomist was trained from each participating state for specimen collection. All samples were centrally tested for analytes. The overall response rate for blood collection was 71.5%. We collected 17 mL of VBS from 3,252 respondents, who consented to participate. Blood samples were tested for routine analytes, and those specific to Alzheimer's Disease (AD) and AD-related dementias (ADRD). Data was reviewed fortnightly. The median cold chain temperature was 6.2°C and hemolysis was seen in 6.7% of the samples. LASI-DAD standardized and implemented VBS collection while overcoming the challenges faced due to India's diverse socio-demographic, geographical, and environmental conditions. This methodology can serve as a robust tool for VBS handling and ensuring high sample quality for future community-based studies.