ABO blood grouping from tear samples: Impact of environmental conditions

Aims: In forensic investigations, ABO blood grouping from biological evidence plays an important role.The aim of this study is to evaluate the feasibility of ABO blood group determination from tear samples and to assess the effect of different environmental conditions on the detectability of ABO antigens.Methods: This is a laboratory-based experimental cross-sectional study.Participants were healthy individuals aged between 18 and 50 years with a known ABO blood group who gave consent for the study and were included in the study.Non-secretor individuals (identified by analyzing saliva samples) or individuals with ocular or oral disorders, have recent eye surgeries and using any eye drops and other eye medications, individuals using oral medication, which can affect the saliva composition were excluded from the study.Tear samples were collected on sterile tissue paper, and each sample was divided into five portions.Samples maintained at room temperature were analyzed immediately (0 hours) and served as the baseline control, while the remaining portions were exposed to low temperature (4 °C), high temperature (56 °C), dry, or moist conditions for 24 hours.ABO blood grouping was performed using the absorption-elution technique.Results: A total of 66 participants were included in the study (mean age: 24.2±6.9years; 51 females [77.3%]).At room temperature the ABO antigens were detected in 57 samples of 66 (86.4%), at low and high temperature it was observed in 55 and 52 of 66 samples (83.3% and 78.8%), in dry and moist condition it was observed in 53 and 43 of 66 samples (80.3% and 65.2%).Cochran's Q test demonstrated a significant overall difference among conditions (Q=11.72,df=4, p=0.0196). Conclusions:The results show that ABO blood group antigens can be successfully detected in tear samples under controlled conditions.However, the reduction in detectability, particularly under moist conditions, highlights the influence of the environment.