1 London, UK and 2 Leeds, UK
EditorWe read with interest the case report by Monte and Lyons1 about the peripartum management of a patient with Glanzmanns thrombasthenia. The report displays how a multi-disciplinary approach to a complicated case can aid in its successful management.
We agree that the thromboelastographic picture of Glanzmanns thrombasthenia has not been reported before. An aspect of the authors discussion that we would like to challenge is their comment that there is no accepted or universally available monitor of platelet function. The PFA-100TM system is a platelet function analyser designed to measure platelet-related primary haemostasis. It has been in use since the mid-1990s.2 In principle, citrated whole blood is aspirated through a capillary into an aperture, the surface of which is coated with collagen to which ADP or epinephrine is added. The time taken for the aperture to occlude by formation of a primary haemostatic plug is measuredthis is the closure time.
Extensive work has been carried out to validate the PFA-100TM in many different patient groups, including patients on anti-platelet agents, patients undergoing cardiopulmonary bypass, and uraemic and cirrhotic patients. A clinical sensitivity of 94.9% and specificity of 88.8% has been found with the PFA, compared with 94.3% and 88.3%, respectively, for platelet aggregometry tests.3 The PFA has been found to be highly reliable in identifying congenital thrombocytopathies, including Glanzmanns thrombasthenia.4
The test is simple, rapid (giving a result within 5 min), and does not require specialist training. Use of the PFA is becoming increasingly widespread and it is now a well-accepted monitor of platelet function in both Europe and North America.
W. Marchant
S. Mallet
London
UK
EditorWe thank Marchant and Mallett for their interest in our case report, and are pleased that they only have one point of criticism.
TEG® measures platelet function in terms of clot strength, determined by the firmness of the fibrin/platelet matrix. The PFA-100TM system measures the ability of platelets to plug a hole in a membrane in terms of closing time. The two tests are complementary. It would have been particularly interesting to see what the PFA would have made of the rFVII, since this would have probably answered the question of its efficacy in this condition. Unfortunately, the nearest PFA that we are aware of is the one in Dr Malletts hospital.
These and other points of care platelet function monitors are reviewed by Harrison,5 and for further information the reader is directed to his review.
S. Monte
G. Lyons
Leeds
UK
References
1 Monte S, Lyons G. Peripartum management of a patient with Glanzmanns thrombasthenia using Thrombelastograph®. Br J Anaesth 2002; 88: 73438
2 Kundu SK, Heilmann EJ, Sio R, Garcia C, Davidson RM, Ostgaard RA. Description of an in vitro platelet function analyser PFA-100. Semin Thromb Haemost 1995; 21: 10612[ISI][Medline]
3 Mammen EF, Comp PC, Gosselin R, et al. PFA-100TM System: A new method for assessment of platelet dysfunction. Semin Thromb Haemost 1998; 24: 195202[ISI][Medline]
4 Muller M, Becker-Hagendorf K, Westrup D, Seifried E, Kirchmaier CM. PFA-100TM system: A sensitive screening test for platelet-related hemostasis defects. Ann Haematol 1997; 74: 72
5 Harrison P. Progress in the assessment of platelet function. Br J Haematol 2000; 111: 73344[ISI][Medline]