The in-vitro bleeding time for the screening of platelet function in the newborn: assessment of a normal reference range

Abstract

Sir: The physiological functional state of platelets in newborn babies is a matter of debate. There is an apparent contrast between an in vitro hypofunctional state of neonatal platelets regarded as subactivated, and evidence of normal or even short in vivo bleeding times. One reason why the problem is still unresolved may be technical since diculties in assessing platelet function in the neonate arise from the excessive volume of blood needed and from the intrinsic variability of the methods available [3,4,6]. Simple ®rst-line screening procedures have not been available to assess the platelet function in newborns. The Platelet Function Analyser (PFA100, Dade Behring, Miami, Fla., USA) is a new tool for the quick and fully automated analysis of platelet response to agonists. The PFA100 measures the``in vitro bleeding time'' (IVBT), an ex vivo surrogate of the in vivo bleeding time, using only 800 ll citrate anticoagulated whole blood. Brie¯y, PFA100 controls the blood ow through a substrate-agonist (collagen-epinephrine or collagen-ADP) coated capillary; platelets adhere, become activated, and form plugs, which obstructs the blood¯ow. The plug-dependent capillary obstruction is measured as closure time. Manual operations are restricted to blood pipetting into disposable cartridges (requiring a few seconds); the overall test time up to the printed report is 10±15 min. The infrareplicate coecient of variation is 7%±12%. IVBT measurement has been successfully used for the detection of congenital platelet disorders such as those due to von Willebrand defect [2]. Owing to its intrinsic characteristics, PFA100 seems to be a candidate to enable large-scale platelet function investigations in newborns. In order to assess the normal newborn IVBT reference range, a group of 25 consecutive neonates was investigated.The study group was homogeneous for gestational age (39 1.2 weeks): all were clinically well, including three from preeclamptic mothers. Mothers and newborns were not on drugs known to aect platelet function. The neonates were bled at 0±4 days of age from the antecubital vein using a 21±23 gauge needle. A total of 36 adult blood donors were used as controls. The results (Fig. 1) clustered according to the newborns' age did not show signi®cant dierences (0 vs 4 days, Kruskal-Wallis analysis). Slight dierences in gestational age did not correlate with closure times (linear regression analysis; epinephrine-induced, EPI, closure time: r 2 = 0.0976, ADP time: r 2 = 0.015). The EPI closure time did not dier between the study groups (EPI time; Mann-Whitney U test: P 0.723). One newborn from a pre-eclamptic woman had the longest closure time of the neonate group (222 s), supporting the hypothesis of a close cause±eect relationship between maternal pre-eclamptic status and neonatal platelet function. A slight dierence was evident comparing the ADP induced closure time of the two groups (ADP time; Mann-Whitney U test: P 0.016).Such ®ndings warrant comment. ADP-dependent platelet activation is a very complex event. Two dis...

Effect of ampicillin on the bleeding time of neonatal intensive care unit patients

“…We highly doubt this possibility, on the basis that the opposite has been reported; namely, bleeding times shorten over the first week after birth. [11][12][13][14] A second limitation in our study is the small numbers of patients studied, and the variability of gestational ages among the study subjects. Third, there is welldescribed operator variability in the bleeding time test.…”

Effect of ampicillin on bleeding time in very low birth-weight neonates during the first week after birth

“…[1][2][3][4][5][9][10][11][12][13] Other tests of platelet function are less applicable for VLBW neonates, principally because of a larger volume of blood needed. These include light transmittance platelet aggregometry, 14 whole-blood aggregometry, 15 multiple electrode aggregometry, 16 thromboelastography 17 and vasodilator-stimulated phosphoprotein phosphorylation.…”

“…1,2 In contrast, very low birth-weight (VLBW, <1500 g) neonates often have subnormal platelet function, and bleeding times that are prolonged, inversely proportionate to their gestational age. [3][4][5] However, over the first 7 to 10 days following birth, the bleeding times of VLBW neonates generally improve (shorten) to about that of term neonates.…”

“…We measured platelet function in two ways, template bleeding time [1][2][3][4][5] and PFA-100 time. [9][10][11][12][13] As was the case in our previous study of ampicillin dosing to late preterm and term neonates, 5 we hypothesized that a few doses of ampicillin would have little effect on platelet function, but that ampicillin treatment for the entire first week would prolong the bleeding time.…”

Ibuprofen lysine administration to neonates with a patent ductus arteriosus: effect on platelet plug formation assessed by in vivo and in vitro measurements

“…The capacity to generate a hemostatically effective platelet plug can be assessed by in vivo methods (template bleeding time) and by in vitro methods (platelet function analyzer (PFA)-100 time). [2][3][4][10][11][12][13][14][15][16][17] We obtained these tests before and at various preset intervals after ibuprofen administration to 20 neonatal intensive care unit (NICU) patients who had a PDA and herein report the results of those studies.…”