Platelet transfusion “Trigger” for lumbar puncture

To the Editor: A treatment recommendation was made at the recent ASPHO meeting (29 April–2 May, San Francisco) that warrants comment. During the session on platelet transfusions in children one of the invited speakers stated that the platelet count should be ‘‘60–80,000’’ before a lumbar puncture (LP) is performed. We are unaware of any data to support this, and are concerned that such a comment could have medicolegal ramifications. In fact, three fairly recent reports suggest that much lower platelet counts should suffice for this procedure, in stable patients (1–3). Mainwaring et al. [1] in 1998 reported data from 83 ALL patients treated at their center from 1987 to 1997. Five of these patients had platelet counts <20,000/ml, and 19 had counts of 20–50,000/ml at the time of their diagnostic LPs. They reported ‘‘blood stained’’ taps in seven, prolonged ‘‘oozing’’ from the puncture site in one (controlled by local pressure), but no neurologic problems in any. They concluded that ‘‘transfusion of platelet concentrates prior to LPs in children with significant thrombocytopenia is not justified as a routine measure. ’’ Howard et al. [2] reported the experience at St. Jude Children’s Research Hospital in 2000, and were not able to demonstrate any risk to ALL patients with platelet counts down to 10,000/ml. The 958 consecutively diagnosed ALL patients from 1984 to 1998 received 5,223 LPs. Twenty nine had the procedure performed at platelet counts <10,000/ml, 170 at counts of 11–20,000/ml, and 742 at counts of 21–50,000/ml. In this extensive retrospective review, they did not detect any significant adverse events in patients getting an LP at a platelet count of 10,000/ml. They concluded: ‘‘prophlactic platelet transfusion is not necessary in children with platelet counts higher than 10,000/ml. ’’ And finally, just last year a report from Switzerland in adult patients with acute leukemia [3] found no serious clinical bleeding in 66 patients, undergoing 195 LPs. The authors recommended that a platelet count of 20,000/ml be the ‘‘trigger’’ point for platelet transfusions before an LP. The one exception to the above might be the ALL patient at diagnosis. There have been two published reports [4,5] suggesting an increased relapse rate in children who had ‘‘traumatic’’ LPs (10 or more red blood cells/ml) with lymphoblasts in the csf sample at their diagnostic evaluation. Since there also is likely an increased risk of a traumatic LP with severe thrombocytopenia, platelet transfusions before the very first LP in children with severe thrombocytopenia might be indicated. The exact platelet count at which this should occur, however, is not clear. Howard et al. [6] suggest that a platelet count of less than 100,000/ml is associated with a significantly increased risk of a traumatic LP (odds ratio of 1.5). Interestingly, they could not demonstrate a significant difference in risk when comparing any subgroups of patients with platelet counts <100,000/ml. It also is of interest that in their large body of experience (5,609 LPs), they had a 29% incidence of traumatic LPs. Our experience is quite different. Over the past 10 years, involving 163 evaluable patients with newly diagnosed ALL there have been only 11 traumatic LPs at diagnosis (6.4% incidence), and 5 of these had red cell counts of only 10– 12. The platelet counts in these patients were 47,000– 239,000/ml with a median of 87,000/ml. We understand a national study regarding platelet dosing in children is being planned. Perhaps this issue of minimum platelet count needed before LPs (and other invasive procedures) could be included in this broad based study. In the meantime, we caution against the creation of practice guidelines for which there are no supporting data.