LONGER APTT VALUES IN HEALTHY-CHILDREN THAN IN ADULTS - NO SINGLE CAUSE

We have shown that activated partial thromboplastin time values in chi ldren are considerably longer than in adults, but the causes for this observation remained unclear. Therefore, we investigated the correlati on between activated partial thromboplastin time values and concentrat ions of clotting factors, quotients and titers of the tissue thrombopl astin inhibition test, and antiphospholipid antibodies in healthy chil dren, children with recurrent infections, and adults. Concentrations o f factors VIII, IX, and HMWK were significantly lower in children than in adults. Simple linear regression analysis failed to show a correla tion between the concentration of a single clotting factor and the act ivated partial thromboplastin time values. No significant correlation was found between activated partial thromboplastin time and elevation of the tissue thromboplastin inhibition test quotients or titers, or a ntiphospholipid antibodies values. The determined activated partial th romboplastin time was best described by a function including all measu red coagulation factors. Our study suggests, that no single clotting f actor or lupus anticoagulants are responsible for the longer activated partial thromboplastin time in healthy children, but that activated p artial thromboplastin prolongation is caused by the combination of sev eral slightly lower clotting factors. (C) 1998 Elsevier Science Ltd.