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CAPILLARY AND VENOUS BLOOD SAMPLES WITH FILTER PAPER SPOTTED BLOOD SAMPLES

Abdulrazzaq YM, Ibrahim A

Faculty of Medicine, UAE University, United Arab Emirates

Objective - To determine the reliability of filter paper spotted blood method to measure amino acids and whether amino acid results thus obtained are reproducible and comparable to the results obtained by measuring plasma amino acids in either capillary or venous blood.

Methods � Blood samples from a finger-prick were collected in capillary tubes and blotted on filter papers; another sample was taken from a vein, from 19 healthy volunteers aged between 18 and 24 years after a strict 12-hour overnight fast. Another 9 healthy adult volunteers provided blood samples on filter papers for the storage study; 9 samples were analyzed immediately; 9, 8 and 4 samples were stored at �20^oC, -4^oc and room temperatures respectively and analyzed after 14 days; 8 samples stored at �20^oC were analyzed after 4 weeks.

Results - Intra-sample reproducibility in the filter paper blood from the same individual was found to be mostly less than 20%, while for the capillary blood was less than 5%. The greatest variability was in cystine and methionine. There was no significant difference between results obtained from capillary blood and from venous blood, but there was a significant difference between amino acid concentrations in venous and capillary blood on the one hand and filter paper blood on the other. Storage at different temperatures and for a varied period of time showed little change except in serine, glutamate, ornithine, histidine, cystine and methionine. There was a 30% decrease in concentrations of most amino acids in filter paper blood when compared to capillary or venous blood probably because of loss in the extraction process.

Conclusion - A new set of values for amino acids in filter paper blood in normal individuals is presented. Blood spotted filter paper could be used to screen practically all inborn errors of amino acid metabolism.