The need for standardized bloodspot TSH-calibrators in congenital hypothyroidism screening

Introduction: The preparation of bloodspot calibrators and quality control samples for neonatal thyrotropin (TSH), as part of the national quality assessment scheme in The Netherlands, is sometimes problematic. Often, the recovery of the added TSH is well above 100% when measured in plasma. Results from other External Quality Assessment Schemes for neonatal TSH show similar problems. Methods and Results: A questionnaire was sent to 17 kit manufacturers and organizers of EQAS concerning the preparation of bloodspot calibrators for TSH; 13 completed questionnaires were returned. There are large differences with respect to type of filterpaper, matrix, assessment of TSH-concentrations to the calibrators, size of the bloodspots, shelf life, etc. Discussion: Attention is focused on several items to be considered when attempting standardization of the preparation of TSH bloodspot calibrators.