Background/aims Preterm infants have higher rates of haemorrhagic diathesis and respiratory complications than terms and adults. Platelets play a key role in haemostasis but detailed platelet function testing in neonate populations are lacking mainly due to the large blood volume requirements. To address this we developed a physiologically relevant assay on vonWillebrand factor that mimics platelet behaviour in vivo at arterial shear conditions.

Methods A prospective clinical study of blood from preterms < 32 weeks (n = 21), terms (n = 12) and adults (n = 48). 200 μl of blood for each donor was labelled with a florescent dye for visualisation of platelets in real-time. The blood was perfused over parallel plate flow chambers coated with purified vonWillebrand Factor (vWF). Platelet interactions with the surface were imaged via video microscopy at high speed (500 frames at 30 frames/second). In-vivo when platelets are exposed to activated vWF they tether, roll and translocate. For the first time ever we managed to image these platelet behaviours using a custom designed platelet tracking algorithm.

Results Preterms had significantly more numbers of static platelets (54 ± 55 vs. 26 ± 4 and 28 ± 2 SEM, p < 0.0001). In the preterm cohort there were increased numbers of platelets translocating on the vWF surface (359 ± 25 vs. 277 ± 25 and 307 ± 10 SEM, p = 0.05) compared with the terms and adults. Clinical outcomes showed significantly high levels of RDS (76.19%), CLD (38.09%) IVH (28.57%) and pulmonary haemorrhage (23.8%).

Conclusions The behaviour of platelets on vWF is significantly different in preterms and could explain the increased tendency to bleeding and development of RDS and CLD in premature neonates. The tiny volume of blood needed to perform this test has major implications for its use in a clinical setting.