Age-associated developmental changes in the activated partial thromboplastin time (APTT) and causes of prolonged APTT values in healthy Chinese children.

Background: The concept of developmental hemostasis has been universally accepted. Physiological reference ranges for coagulation tests are available for infants and children of different ages. However, on Oriental children they are rare.

Methods: Results of preoperative activated partial thromboplastin time (APTT) in neonates, infants, children aged 1-18 years and adults with minor elective surgery in a university affiliated hospital were reviewed retrospectively. Plasma activity of factors VIII, IX, XI, XII (FVIII:C, FIX:C, FXI:C, FXII:C) and lupus anticoagulants (LAC) in 47 children with prolonged APTT and 34 adult controls were measured to investigate the causes of prolongation.

Results: Compared with adults, APTT values were prolonged significantly and were age-dependent in children, especially in neonates and infants aged 1-6 months. Mean values for FXII:C and FIX:C in children with prolonged APTT values were significantly lower than those in adults (p<0.001). Prolonged APTT values correlated negatively with FXII:C and FIX:C, and weakly with the LAC Screen ratio (LAC-SR) (r(0.01)=-0.808, -0.705 and 0.372, p=0.000, 0.000 and 0.001, respectively). There was weak negative correlation between FXII:C and LAC-SR (r(0.01)=-0.277, p=0.012). No significant correlation was seen between prolonged APTT values and FVIII:C or FXI:C.

Conclusions: APTT values change dynamically with age during childhood and display a distinct pattern of evolution in children. Lower values of FXII:C and FIX:C, and presence of LAC contribute to the prolongation of APTT values in Chinese children.