Factors influencing dry blood specimens of filter paper in newborn screening assay

Objective To investigate factors influencing thyroid stimulating hormone (TSH) and phenylalanine (phe) assay in dry blood spots on filter paper. Methods The influence on enzyme linked immunoassays and bacterial inhibition assay were studied so as to control their changes. Results Many influencing factors were noted in newborn screening assay. TSH results were stable if specimens were collected form newborns 72 hours after delivery. Different results were obtained when TSH was tested in different seasons. Specimens were air dried at room temperature before transportation. To reduce false positive phe result, specimens were collected from newborns 72 hours after delivery. The phe result was very stable with a plating temperature of 55 60℃ and speradical distribution of blood spots . Conclusion To assure the quality of screening the time of specimens collecting, different cut off, blood spots disposition and best condition should be controlled.