Patsy Vegh

Home monitoring of warfarin therapy in children with a whole blood prothrombin time monitor

We prospectively evaluated a capillary whole blood prothrombin time (PT) monitor (Biotrack, Ciba Corning) in an outpatient pediatric anticoagulation clinic (40 clinic patients) and in age-matched healthy subjects (30 control subjects). Subsequently, 23 children requiring warfarin therapy were placed on a home program (home patients) using the PT monitor; their parents were trained and the results followed by clinic staff. The PT results were reported as internationalized normalized ratios (INRs). The laboratory and PT-monitor INR values were similar for the clinic patients and the control subjects (y = 0.76x + 0.38; r = 0.93; p < 0.001). The accuracy of the PT monitor (the difference between INR values and the laboratory INR) was best at an INR of 2.5 to 3.5; 90% of paired INR values were within 0.8 INR units. The average duration of monitoring for home patients was 13 months (range, 2 to 60 months). They had an average of 3 dose measurements (range, 1 to 11 measurements) and 1.8 dose changes (range, 0.6 to 4.5 changes) per month. Of the 599 measurements, 63% were within the therapeutic range, similar to those for clinic patients; the dose requirements were also similar. There was 1 significant bleeding event, a subdural hematoma in a patient with an INR of 4.1, and 1 catheter-related thrombotic event with an INR of 1.2; both children recovered. Of the 23 families, one discontinued home monitoring because of parental discomfort, 2 children died of their primary disease, 6 completed warfarin therapy, and 14 remain on the home program. We conclude that the whole blood PT/INR monitor is safe and offers practical advantages to children requiring anticoagulation.

The Relationship of Antiphospholipid Antibodies to Thromboembolic Events in Pediatric Patients with Systemic Lupus Erythematosus: A Cross-Sectional Study

The purpose of this study was to evaluate pediatric patients with systemic lupus erythematosus (SLE) to determine 1) the incidence of thrombosis, 2) the incidence of antiphospholipid antibodies, and 3) whether there is an association between the presence of antiphospholipid antibodies and thrombosis. We performed a cross-sectional cohort study in 59 consecutive SLE patients who had been managed at rheumatology clinics in two pediatric hospitals. A history, questionnaire, and chart review were completed by the study nurse blinded to laboratory results. Only the thrombotic events that could be substantiated by review of radiographic tests were accepted. The presence of antiphospholipid antibodies was determined by prospective analysis for a lupus anticoagulant and anticardiolipin antibodies on two separate occasions at least 3 mo apart. Patients were considered to be positive if one or more tests were positive on both occasions. Thirteen thrombotic events occurred in 10 of the 59 patients(17%). Fourteen patients (24%) were classified as positive for lupus anticoagulant, and 19 patients (27%) were classified as positive for anticardiolipin antibodies. A significant relationship between the presence of a lupus anticoagulant and a thrombotic event was shown: odds ratio 28.7(95% confidence interval 4.03-138.2, p < 0.001). A nonsignificant trend was seen for the presence of an anticardiolipin antibody and a thrombotic event: odds ratio 2.12 (95% confidence interval 0.71-22.8,p = 0.08). We conclude that in pediatric patients with SLE:1) a significant proportion of patients have thrombotic events,2) a significant proportion of patients have antiphospholipid antibodies, and 3) there is a significant relationship between the presence of a lupus anticoagulant and thrombotic events.

A multicenter study of the treatment of childhood chronic idiopathic thrombocytopenic purpura with anti-D

We evaluated the effects of the intravenous administration of anti-D, an immune globulin directed at the D antigen on erythrocytes that is purified from plasma from sensitized persons, on patients with idiopathic thrombocytopenic purpura. To determine the most effective dose, the duration of response, and the side effects of this therapy in children, we performed a multicenter cohort study of escalating doses of intravenously administered anti-D in children aged 1 to 18 years with chronic idiopathic thrombocytopenic purpura, defined as idiopathic thrombocytopenic purpura persisting for more than 6 months with a platelet count of less than 50 x 10(9) cells/L. Twenty-five Rh-positive children received increasing doses of anti-D as follows: day 1, 25 micrograms/kg; day 2, 25 micrograms/kg; day 7, 35 micrograms/kg; day 14, 45 micrograms/kg; and day 21, 55 micrograms/kg. Administration of anti-D was stopped after day 21 or when the platelet count rose to greater than 150 x 10(9) cells/L or the hemoglobin level was 100 gm/L. Platelet count was less than 50 x 10(9) cells/L in all children before treatment. A response was defined as an increase in the platelet count to more than 50 x 10(9)/L and a doubling of the pretreatment platelet count. Of 25 children, 23 (92%) had responses by day 7 of the initial treatment protocol. Eighteen children (72%) had platelet counts greater than 150 x 10(9) cells/L by day 7 after two doses of anti-D. Median duration of response was 5 weeks (range 1 to 24 weeks). Average drop in hemoglobin level was 13.7 gm/L; in one child (a nonresponder) hemoglobin value fell to less than 100 gm/L. No other untoward side effects were seen. Of the 23 children who responded, 21 were retreated with one dose of anti-D when platelet counts returned to baseline values of less than 50 x 10(9) cells/L; all but three of the children who underwent retreatment showed a response the second time. Sixteen children continued to receive intermittent anti-D therapy after completion of the study, and all continued to have excellent responses. We conclude that anti-D is a safe, effective, and relatively inexpensive therapy for childhood chronic idiopathic thrombocytopenic purpura.

Dose-finding and pharmacokinetics of therapeutic doses of tinzaparin in pediatric patients with thromboembolic events.

In children, there is an increasing off-label use of low molecular weight heparin (LMWH). However, there is an absence of information on dosing and pharmacokinetics of LMWH over all age groups. The objectives of the current study were to determine i) the once daily dose required to achieve anti-Xa levels of 0.5-1.0 IU/mL, ii) the pharmacokinetics and iii) preliminary safety data using tinzaparin. The study took the form of a single centre open-label Phase II study performed in 35 children requiring anticoagulation for treatment of thromboembolism. Age groups studied were: 0- < 2 months; 2 months- < 1 year; 1- < 5 years; 5- < 10 years; 10-16 years. Both population pharmacokinetic analysis using nonlinear mixed-effect modeling techniques and model-independent pharmacokinetic methods were employed. Results showed a relationship of age and dose requirements, clearance, time to peak anti-Xa level and volume of distribution. Younger children required an increased dose, cleared tinzaparin more rapidly, had anti-Xa levels peak earlier and had an increased volume of distribution. Younger children were more likely to be below target range than older children,with up to 75% of children < 1 year being below the target anti-Xa level. Four recurrences and one major bleed occurred. In conclusion, there is an inverse relationship of age on dose requirements related to volume of distribution, clearance and time to peak anti-Xa. Children < 5 years likely require dose adjustment samples to be drawn 2-3 hours post injection. Infants require anti-Xa levels to be monitored at least twice monthly.

Coagulation screening tests in high risk neonates: a prospective cohort study.

Forty seven infants in a prospective cohort of 170 high risk neonates without signs of overt bleeding had abnormal coagulation screening tests within 36 hours of birth. Early thrombocytopenia was a better predictor of prolonged prothrombin times and hypofibrinogenemia than very low birth weight, fetal growth retardation, or poor five minute Apgar scores.

THE RELATIONSHIP OF ANTIPHOSPHOLIPID ANTIBODIES TO THROMBOEMBOLIC DISEASE IN SYSTEMIC LUPUS ERYTHEMATOSUS IN CHILDREN: A CROSS-SECTIONAL STUDY.▴ 899

THE RELATIONSHIP OF ANTIPHOSPHOLIPID ANTIBODIES TO THROMBOEMBOLIC DISEASE IN SYSTEMIC LUPUS ERYTHEMATOSUS IN CHILDREN: A CROSS-SECTIONAL STUDY. ▴ 899