Thrombotic thrombocytopenic purpura/haemolytic uraemic syndrome: a new index predicting response to plasma exchange.

Despite the favourable response of thrombotic thrombocytopenic purpura/haemolytic uraemic syndrome (TTP/HUS) to plasma exchange, an early level of mortality persists. Non-response has been associated with a low frequency of exchange. The Rose index of TTP/HUS severity, occasionally used to predict the response of TTP/HUS to plasma exchange, remains unsatisfactory. The purpose of this study was to develop a new index predicting response of TTP/HUS to plasma exchange and to compare it with the Rose index. Retrospective analysis of 171 cases of TTP/HUS from 39 apheresis units across Canada between 1980 and 2001 was conducted. Logistic regression analysis was used to derive a model predicting 6-month mortality from presenting characteristics. The reduced model contained age >40 years, haemoglobin <9.0 g/dl and the presence of a fever at presentation. Gender, platelet count, creatinine and neurological signs were not part of the final model. This model predicted 13.4% of outcome variance. Predictive scores of 0, 2, 4 and 6 correlated with 6-month mortality rates of 12.5%, 14.0%, 31.3% and 61.5% respectively in our source population. This simple model may help identify those patients who would benefit from higher treatment intensity.

A review of research related to blood transfusion in Canada, 2000-2002.

The former National Blood Safety Council undertook a comprehensive review of blood transfusion research in Canada for the years 2000 through 2002. Data were acquired by direct contact with agencies which support such research and by searches of the relevant websites. Total grant support increased markedly over the 3-year period, from 4.1 million dollars to 18.5 million dollars. Publicly funded granting agencies, biopharmaceutical companies, the blood services and the province of Ontario were major supporters. Much smaller amounts were granted from charitable organizations. Clinical research attracted the majority of the funding, although a larger number of projects were basic science in nature. Most research was carried out in the provinces of Ontario, Québec and British Columbia. Although we have not assessed the productivity of blood-related research, it appears that substantial amounts of funding were allocated to these projects between 2000 and 2002. These data may provide a helpful perspective to investigators in transfusion medicine elsewhere, who may also be assessing the relative priority given to this field of research in their own countries.

Therapeutic plasma exchange: an update from the Canadian Apheresis Group.

In 1997, the Canadian Apheresis Group reviewed data on 103,416 plasma exchange procedures that had been collected since 1980. Although the number of plasma exchanges gradually increased (from 3189 to 8208 per year), the pattern changed. In 1981, the five most frequent indications for plasma exchange resulted in 55% of all such procedures; by 1997, the five most frequent indications for plasma exchange resulted in 81.1% of all such procedures. During this period, three conditions that were originally among the most frequent indications for plasma exchange became among the least frequent. This paper reviews the published evidence that supports or refutes the use of plasma exchange in the category of the five most frequent indications from 1981 to 1997: thrombotic thrombocytopenic purpura, myasthenia gravis, chronic inflammatory demyelinating polyneuropathy, Waldenstrom macroglobulinemia, the Guillain-Barre syndrome, rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis. For most disorders, use of plasma exchange procedures is correlated with published evidence, and the changing patterns of plasma exchange use by members of the Canadian Apheresis Group reflect published evidence. Annual center-by-center reviews of use of plasma exchange may also have influenced practice patterns.

Genetic determinants of heritable venous thrombosis: genotyping methods for factor V(Leiden)A1691G, methylenetetrahydrofolate reductase C677T, prothrombin G20210A mutation, and algorithms for venous thrombosis investigations.

OBJECTIVES: To implement cost effective and clinically relevant thrombophilic genotyping and homocysteine analysis in our coagulation laboratory. METHODS: We describe genotyping assays for three of the genetic defects associated with hereditary thrombosis: factor V(Leiden) A1691G, methylenetetrahydrofolate reductase C677T, and prothrombin gene G20210A. A second confirmatory assay for factor V(Leiden) using allele specific oligonucleotide polymerase chain reaction is also presented. We suggest an algorithm for the rational integration of the traditional assays routinely used to investigate venous thrombosis with genotyping and plasma homocysteine measurements. RESULTS: These polymerase chain reaction based assays were designed to be performed under identical reaction conditions, permitting simultaneous setup, amplification, digestion, and analysis. CONCLUSIONS: The three genotyping assays presented are robust and relatively easy to perform. Use of an algorithm will ensure efficient resource utilization and minimize unnecessary testing.

Interaction between fenofibrate and warfarin.

OBJECTIVE: To determine whether the potentiation of warfarin's anticoagulation effect, which occurred in two patients, was due to an interaction with fenofibrate. CASE SUMMARY: Two patients developed significant potentiation of the anticoagulant effect of warfarin while receiving fenofibrate. In one patient we followed published guidelines to test the potential interaction, including rechallenge twice, and measurements of factors II, V, and VII and liver enzymes to ensure the authenticity of the interaction. We confirmed the interaction by noting that the international normalized ratio (INR) increased with rechallenge, the clotting factor concentrations decreased in concert with the INR, and no other laboratory or clinical factors accounted for this potentiation of the oral anticoagulant affect. DISCUSSION: We previously developed criteria specifically for determining the strength of inferred causation in reports of drug interactions with oral anticoagulants; these criteria were adapted from previously described principles of causality assessment. Our observations in two patients suggest a "highly probable" potentiating interaction between fenofibrate and warfarin. Our data do not allow us to draw definitive conclusions on a mechanism of interaction, but fenofibrate is an oral antilipemic agent, similar to clofibrate, that has been described as potentiating oral anticoagulants by affecting coagulation factor synthesis, likely by altering receptor synthesis. Our finding of lower concentrations of coagulation factors suggests a similar mechanism for fenofibrate. Recent data suggest that lipid lowering is effective for primary and secondary prevention of cardiac events. One might therefore expect to see an increase in the use of the various lipid-lowering agents in patients who receive long-term anticoagulation. Our results indicate that the potential for an exaggerated anticoagulant effect occurs within 5-10 days in patients treated with fenofibrate who are receiving long-term anticoagulation with warfarin. CONCLUSIONS: Fenofibrate potentiates the effect of warfarin. Serial monitoring of the INR, at least three times per week, is therefore strongly recommended when initiating fenofibrate therapy in patients receiving warfarin.

Hematological and lipid changes in newborn piglets fed milk-replacer diets containing erucic acid.

Canola oil is not presently permitted in infant formulations in the United States because of lack of information concerning the effects of feeding canola oil to the newborn. We have previously reported a transient decrease in platelet counts and an increase in platelet size in newborn piglets fed canola oil for 4 wk, and have confirmed this in the present study. In canola oil-fed piglets, changes in platelet size and number were overcome by adding either long-chain saturated fatty acids from cocoa butter (16:0 and 18:0), or shorter-chain saturates from coconut oil (12:0 and 14:0). Feeding a high erucic acid rape-seed (HEAR) oil, with 20% 22:1n-9, led to an even greater platelet reduction and increased platelet size throughout the 4-wk trial. Bleeding times were longer in piglets fed canola oil or HEAR oil compared to sow-reared and soybean oil-fed piglets. There were no other diet-related changes. Diet-induced platelet changes were not related to platelet lipid class composition, but there were fatty acid changes. The incorporation of 22:1n-9 into platelet phospholipids of piglets fed canola oil was low (0.2-1.2%), and even for the HEAR oil group ranged from only 0.2% in phosphatidylinositol to 2.4% in phosphatidylserine. A much greater change was observed in the concentration of 24:1n-9 and in the 24:1n-9/24:0 ratio in platelet sphingomyelin (SM). The 24:1n-9 increased to 49% in the HEAR oil group compared to about 12% in animals fed the control diets (sow-reared piglets and soybean oil-fed group), while the 24:1n-9/24:0 ratio increased from about 1 to 12. Even feeding canola oil, prepared to contain 2% 22:1n-9, led to a marked increase in 24:1n-9 to 29% and had a 24:1n-9/24:0 ratio of 5. The canola oil/cocoa butter group, which also contained 2% 22:1n-9, showed a lower level of 24:1n-9 (20%) and the 24:1n-9/24:0 ratio (3) compared to the canola oil group. The results suggest that the diet-related platelet changes in newborn piglets may be related to an increase in 24:1n-9 in platelet SM, resulting from chain elongation of 22:1n-9. The inclusion of canola oil as the sole source of fat in the milk-replacer diets of newborn piglets resulted in significant platelet and lipid changes.

Changes in activated protein C resistance during normal pregnancy.

OBJECTIVE: The objective of this study was to determine the changes in activated protein C resistance that occur during normal pregnancy. STUDY DESIGN: In this cross-sectional study activated protein C was measured in 128 women with normal pregnancies in the first, second, and third trimesters and in nonpregnant control subjects with 24 to 39 women in each group. In addition, factor V, factor VIII, free protein S, and functional protein C were measured and correlated with activated protein C levels. Polymerase chain reaction for factor V Leiden mutation was performed. RESULTS: There was a significant fall in the activity of activated protein C in the second and third trimesters of pregnancy (p < 0.05). This was related to increased factor VIII and decreased free protein S levels (p = 0.002, R2 = 0.20). The prevalence of the factor V Leiden mutation was 7.3%. CONCLUSION: Resistance to activated protein C is increased in the second and third trimesters of pregnancy. This is related to the alterations in other coagulation proteins, a phenomenon normally occurring during pregnancy.

Late relapses in patients successfully treated for thrombotic thrombocytopenic purpura. Canadian Apheresis Group.

OBJECTIVE: To determine the incidence and timing of relapses in patients who have recovered from an acute episode of thrombotic thrombocytopenic purpura. DESIGN: Clinical follow-up for 3 to 10 years. SETTING: General community outpatient study; patients who had relapse were hospitalized. PARTICIPANTS: 63 of 72 surviving patients who had participated in a randomized study that compared plasma exchange and plasma infusion as treatments for thrombotic thrombocytopenic purpura and for whom continued clinical follow-up was obtained. OUTCOME MEASURES: Recurrence of thrombotic thrombocytopenic purpura as defined by a decrease in platelet count to less than 100 x 10(9)/L and by the onset of microangiopathic hemolytic anemia as identified by erythrocyte fragmentation in a peripheral blood film. RESULTS: 37 of the 63 patients have not had recurrence of thrombotic thrombocytopenic purpura and have remained completely well; 6 patients have not had recurrence but have developed other medical problems; 3 patients have not had recurrence but have residual neurologic defects from the original episode; and 17 patients have had one or more recurrences, occurring 7 months to 8 years after the original episode. As determined by Kaplan-Meier analysis, the projected recurrence rate after 10 years in all surviving patients is 36% (95% CI, 23% to 59%). CONCLUSIONS: More than one third of patients who survive an acute episode of thrombotic thrombocytopenic purpura will have at least one relapse during the following 10 years.

Hematological and lipid changes in newborn piglets fed milk replacer diets containing vegetable oils with different levels of n-3 fatty acids.

To test if linolenic acid (18:3n-3) from vegetable oils would affect bleeding times and platelet counts in newborns, piglets were used as a model fed milk replacer diets containing 25% (by wt) vegetable oils or oil mixtures for 28 d and compared to sow-reared piglets. The oils tested included soybean, canola, olive, high oleic sunflower (HOAS), a canola/coconut mixture and a mixture of oils mimicking canola in fatty acid composition. All piglets fed the milk replacer diets showed normal growth. Bleeding times increased after birth from 4-6 min to 7-10 min by week 4 (P < 0.001), and were higher in pigs fed diets containing 18:3n-3, as well as in sow-reared piglets receiving n-3 polyunsaturated fatty acids (PUFA) in the milk, as compared to diets low in 18:3n-3. Platelet numbers increased within the first week in newborn piglets from 300 to 550 x 10(9)/L, and remained high thereafter. Milk replacer diets, containing vegetable oils, generally showed a transient delay in the rise of platelet numbers, which was partially associated with an increased platelet volume. The oils showed differences in the length of delay, but by the third week of age, all platelet counts were > 500 x 10(9)/L. The delay in rise in platelet counts appeared to be related to the fatty acid composition of the oil, as the effect was reproduced by a mixture of oils with a certain fatty acid profile, and disappeared upon the addition of saturated fatty acids to the vegetable oil. There were no alterations in the coagulation factors due to the dietary oils. Blood plasma, platelets and red blood cell membranes showed increased levels of 18:3n-3 and long-chain n-3 PUFA in response to dietary 18:3n-3. The level of saturated fatty acids in blood lipids was generally lower in canola and HOAS oil-fed piglets as compared to piglets fed soybean oil or reared with the sow. The results suggest that consumption of milk replacer diets containing vegetable oils rich in 18:3n-3 does not represent a bleeding risk, and that the transient lower platelet count can be counterbalanced by the addition of saturated fatty acids to the vegetable oils.

Comparison of plasma exchange with plasma infusion in the treatment of thrombotic thrombocytopenic purpura. Canadian Apheresis Study Group.

BACKGROUND: Thrombotic thrombocytopenic purpura is an uncommon disease with a high mortality rate even with current treatment. The cause of the syndrome and its optimal treatment are unknown. Although both plasma exchange and plasma infusion have been useful treatments, it is not clear which is superior. In this report we describe a prospective randomized trial comparing plasma exchange with plasma infusion for the treatment of thrombotic thrombocytopenic purpura. METHODS: One hundred two patients with thrombotic thrombocytopenic purpura were randomly assigned to receive either plasma exchange or plasma infusion with fresh-frozen plasma on seven of the first nine days after entry into the trial. The total volume of plasma received by patients undergoing plasma exchange was three times that received by patients undergoing plasma infusion. All the patients also received aspirin and dipyridamole. The outcomes in the two groups were compared at the end of the first treatment cycle (day 9) and after six months. RESULTS: At the end of the first treatment cycle patients receiving plasma exchange had a higher rate of response as defined by an increase in the platelet count (24 of 51 patients) than those who received plasma infusion (13 of 51, P = 0.025). Of the 51 patients treated with plasma exchange, 2 died, whereas 8 of the 51 patients who received plasma infusion died (P = 0.035). After six months the outcome in the plasma-exchange group was still superior, with a response observed in 40 of 51 patients, whereas 25 of 51 patients in the plasma-infusion group responded (P = 0.002). Eleven patients in the plasma-exchange group died, as did 19 patients in the plasma-infusion group (P = 0.036). The overall mortality was 29 percent. CONCLUSIONS: Plasma exchange is more effective than plasma infusion in the treatment of thrombotic thrombocytopenic purpura.

Plasma exchange in Canada. The Canadian Apheresis Study Group.

Since 1982 the Canadian Apheresis Study Group (CASG) has collected data on plasma exchange activities in Canada. In 1987, 5907 such procedures were carried out on 700 patients for more than 22 different diseases; this represented an increase of 28% over the figure for 1982. A shift in activity has occurred over the years; originally hematologic disorders accounted for most of the procedures; however, in 1987, 60% of the exchanges were done to treat neurologic disorders, mainly myasthenia gravis and acute and chronic Guillain-Barré syndrome. Several prospective randomized clinical trials have recently been completed by the CASG in the hope of determining the optimal application of plasma exchange. These studies, currently under review, include 168 patients with multiple sclerosis, 100 with thrombotic thrombocytopenic purpura and 43 with rapidly progressive glomerulonephritis. Reactions occur in 12% of cases; they are usually minor and are limited to circumoral paresthesia, mild hypertension or hypotension and hives.

Intensive plasma exchange therapy in ten patients with idiopathic thrombocytopenic purpura.

Intensive plasma exchange therapy with fresh-frozen plasma as the replacement fluid was used to manage ten patients, five with acute and five with chronic immune thrombocytopenic purpura (ITP). Therapy was started because of severe hemorrhage (1 case), failure to respond to steroid therapy (6 cases), or steroid dependence (3 cases). After a median of four exchanges over 6 days (median total volume removed, 11.7 liters), initial responses, defined as a platelet count greater than 100,000 per microliter at the end of the exchange series, were observed in 80 percent of the patients treated. Two adolescents, ages 16 and 17 years, with chronic ITP failed to respond to plasma exchange therapy and subsequently responded to splenectomy. Prolonged remissions of 9 months and greater than 2 years were observed in two patients with acute ITP; in patients with chronic ITP, no prolonged remissions occurred. Neither pre-exchange levels of platelet-associated immunoglobulin G (PAIgG) nor circulating immune complexes predicted the response to plasma exchange, although serially determined PAIgG levels correlated with the severity of ITP and response, or lack of response, to plasma exchange. We conclude that intensive plasma exchange merits further study in patients with acute ITP unresponsive to steroid therapy to determine if the need for splenectomy is reduced. In selected patients with chronic ITP, exchange therapy may provide short-term adjunctive benefit.

Morphometric analysis of platelets in Bernard-Soulier syndrome: size and configuration in patients and carriers.

Quantitative ultrastructural morphometric analysis has been carried out on thin sections of platelets from two Bernard-Soulier sisters and their parents. Measurements were made for the major and minor axes, axial ratios, cross-sectional circumference and cross-sectional area. Platelets were collected either into CPD anticoagulant or directly into glutaraldehyde. The results confirm that Bernard-Soulier platelets are significantly larger than normals (p less than 0.05) in all the parameters mentioned and indicate (I) that the morphology of platelets from Bernard-Soulier patients is affected by the presence of anticoagulant, and (II) a more spherocytic configuration is characteristic of Bernard-Soulier disease both in patients and carriers.