CLEIA of humor vitreous in a case of suicidal insulin overdose

•Evidence in insulin overdoses is still a challenge for forensic pathologists.•Serum sample is the gold standard for biochemistry analysis.•Vitreous humor can be considered a reliable alternative matrix for biochemical analysis.•CLEIA is an encouraging analytical method to be considered. Insulin overdoses have been mostly described in literature as accidental and suicidal deaths, especially in diabetic patients. The present case study deals with a 68 years old male found dead in his bedroom. The victim worked as health care professional in a rescue team, suffering from depression for several years. At the death scene, two ampoules of soluble insulin were recovered close to the body, one of which was empty. At autopsy, no signs of trauma and no injection marks were found at common sub-cutaneous or intravenous injection sites. No other remarkable findings, but hemorrhagic pulmonary edema along with astrogliosis and neuronal degeneration/necrosis in the subcortical regions and corpus callosum were observed. The blood specimen was inadequate due to hemolysis, since it was not centrifugated soon after sampling. Biochemical analysis was performed on bilateral samples of vitreous humor by using electro-chemiluminescence immunoassay (CLEIA). The insulin concentration was 61.11 mU/L in the right vitreous humor and 74.23 mU/L in the left one; the C-peptide concentration was 0.166 ng/mL in right vitreous and 0.157 ng/mL in the left one. The results are in agreement with levels of insulin and C-peptide detected in previous case studies. Based on these findings the cause of death was determined as suicidal insulin overdoses probably by sublingual administration. This way of self-administration was a diagnosis for exclusion as it has been demonstrated that sublingual human insulin has hypoglycemic effects similar to insulin injected. The case study emphasizes the potential role of vitreous humor as reliable alternative substrate for biochemical analysis compared to post-mortem serum or blood samples in cases of fatal insulin intoxication. Furthermore, the CLEIA is an encouraging analytical method to be considered in such cases, although still not validated to perform quantitative analysis of post-mortem fluids.