Development of saliva-based cTnI point-of-care test: a feasibility study

Abstract

Abstract Background Cardiac troponin is the biomarker of choice for detection of myocardial injury. There is a great need for simple point of care troponin testing among patients with chest pain, mainly in the prehospital setting. In this preliminary study we evaluate the feasibility of a novel, saliva-based cTn test. Aim 1) To evaluate the presence of cTnI in saliva of patients with myocardial injury. 2) To explore the feasibility a saliva-based point-of-care cTn assay. Methods Saliva samples were collected from 32 patients with myocardial injury who tested positive for conventional cTnT blood tests, and from 13 healthy volunteers. 25 and 9 of these samples, respectively, were subjected to a series of advanced saliva processing procedures: “Amplification buffer” – A unique and complex composition which removes a broad spectrum of saliva inhibiting elements of physical, chemical and biological nature. “Hampering remover” – A device which specifically removes salivary alpha amylase that constitutes ∼50% of the total saliva protein content and therefore increases the detection sensitivity of less concentrated components. “Saliva Concentrator Cartridge” – based on the principles of solid phase extraction cartridges and allows rapid and easy analytes concentration. Processed and unprocessed samples were tested with blood cTnI RDT (Troponin I Rapid Test. specifications: detection limit 1ng/mL of whole-blood; Sensitivity: 95.8%; Specificity: 99.7%). Results were interpreted independently by two investigators and only concordant readouts were included in the analyses. Results were compared to blood cTnT levels Results Among the 25 positive samples subjected to advanced saliva processing procedures, 21 were confirmed positive by both investigators (sensitivities of 84%). All 4 negative saliva samples were obtained from patients with relatively low blood cTnT levels of 155 ng/L or less. Testing untreated samples, only 2 out of 32 were positive (sensitivities of 6.25%). In both processed and unprocessed samples no false positive results were seen among healthy individuals (0 out of 9 and 0 out of 13, respectively), corresponding to a specificity of 100% for both processed and unprocessed groups. The negative predictive values for processed and unprocessed groups were 69.23% and 30.23 respectively. Statistical accuracies were 88.24% for the processed group and 33.33% for the unprocessed group. Conclusion This preliminary work demonstrates for the first time the presence of cTnI in saliva of patients with myocardial injury and possible detection of cTnI in clinical saliva samples utilizing a commercial blood-RDT platform. Further research is needed to determine the time activity of troponin in saliva as well as its sensitivity and specificity for myocardial injury. Funding Acknowledgement Type of funding source: Private company. Main funding source(s): Salignostics LTD