Idiopathic osteonecrosis, hypofibrinolysis, high plasminogen activator inhibitor, high lipoprotein(a), and therapy with Stanozolol.

In five patients with idiopathic osteonecrosis (ON) of the hip, four having hypofibrinolysis mediated by high plasminogen activator inhibitor (PAI-Fx), and one with high Lp(a), our specific aim was to determine whether therapy (Rx) with the anabolic-androgenic steroid, Stanozolol (6 mg/day), would normalize PAI-Fx and Lp(a) and thus potentially ameliorate ON. Prior to Rx, none of the four patients with high PAI-Fx could normally elevate tissue plasminogen activator (tPA-Fx) after 10 min venous occlusion at 100 mm Hg. After 12-18 weeks on Rx, PAI-Fx and stimulated tPA-Fx normalized in all four patients. Prior to Rx, mean (SD) stimulated tPA-Fx was low, 0.4 +/- 0.3 IU/ml (lower limit of normal 2.28 IU/ml). On Rx, stimulated tPA-Fx normalized, rising to 2.83 +/- 1.9 IU/ml, P = .004. Prior to Rx, mean (SD) basal PAI-Fx was high, 99 +/- 68 (upper limit of normal 26.9 U/ml), and fell on Rx to 22.5 +/- 22, P = .004. In two of the five patients normalization of hypofibrinolysis or high Lp(a) was accompanied by major symptomatic improvement. Prior to Rx, and 2 years after onset of unilateral hip pain, one of the four patients with high PAI-Fx and low stimulated tPA-Fx could walk only one block painfully. After 8 weeks on Stanozolol Rx, and continuing through 54 weeks on Rx, he walked 2 miles per day without pain, despite radiographic progression of ON. In three of the four patients with high PAI and with osteonecrosis present 0.3, 2, and 6 years prior to Stanozolol Rx, there was no clinical improvement after 14-156 weeks of Rx despite normalization of stimulated tPA-Fx and PAI-Fx. The fifth patient, 1 month after onset of disabling hip pain, had normal PAI-Fx but high Lp(a) (27 mg/dl), and MRI evidence of bone marrow edema ("transient osteoporosis").(ABSTRACT TRUNCATED AT 250 WORDS)

Hypofibrinolytic and atherogenic risk factors for stroke.

In 87 patients (studied on average 1 year after their strokes) and 26 of their first-degree relatives, our specific aim was to assess the prevalence of the following stroke risk factors: hypofibrinolysis, familial hypofibrinolysis, high lipoprotein (a) level, and dyslipidemia. At least 2 months after their strokes (primarily ischemic), 87 patients had measures of lipids and lipoprotein (a); 69 and 67 patients had measures of basal and stimulated fibrinolytic activity, respectively, four new findings were as follows. (1) Hypofibrinolysis was common, with bottom decile-stimulated tissue plasminogen activator activity (the major stimulator of fibrinolysis) in 21% of stroke probands and in 30% of their first-degree relatives, versus 7% of 29 nomolipidemic control subjects (p = 0.09 and 0.026, respectively). (2) The hypofibrinolysis was mediated by top-decile levels of basal plasminogen activator inhibitor activity (the major inhibitor of fibrinolysis), which were observed in 20% of stroke probands and in 21% of their first-degree relatives, versus 8% of 175 nomolipidemic control subjects (p = 0.007 and 0.04, respectively). Mean (SD) basal plasminogen activator inhibitor activity and antigen level were higher in stroke probands (18 +/- 18 U/ml and 35 +/- 31 ng/ml, respectively) than in the 175 normolipemic control subjects (14 +/- 10 [p = 0.002], 28 +/- 34 [p = 0.016]). (3) Levels of basal tissue plasminogen activator antigen, a probable marker for atherosclerosis, were much higher in stroke probands than in the 175 normolipemic control subjects (15 +/- 7.3 ng/ml vs 7 +/- 3.8, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Beta blockers, Lp(a), hypertension, and reduced basal fibrinolytic activity.

To assess the hypothesis that beta blocker use and hypertension are associated with high lipoprotein(a) [Lp(a)] or with reduced basal fibrinolytic activity, the authors studied relationships of hypertension and beta blockers to Lp(a), lipids, lipoproteins, apolipoproteins, and basal fibrinolytic activity in 385 patients consecutively referred for diagnosis and therapy of hyperlipidemia. A second aim was to determine possible gender differences in fibrinolytic activity among patients with hypertension. Ninety-nine patients (58 women [88% post-menopausal] and 41 men) had drug-treated hypertension. In women, hypertension was a positive, independent predictor of the major inhibitors of fibrinolysis, plasminogen activator inhibitor antigen (p = 0.017), and plasminogen activator inhibitor activity (p = 0.004). In men and women, major risk factors for atherosclerosis were significant, independent predictors of reduced basal fibrinolysis. Median Lp(a) in the 99 patients with hypertension (16 mg/dL) did not differ from Lp(a) (18 mg/dL) in normotensive patients (p > 0.1). Of the 385 patients, the 39 beta blocker users had higher plasminogen activator inhibitor activity (p = 0.01), higher triglyceride (p = 0.02) levels, and higher Quetelet Indices (p = 0.01) than non-users (n = 346). After covariance adjusting for age, Quetelet Indices, sex, and triglycerides, plasminogen activator inhibitor activity was not higher in beta blocker users than in non-users (p > 0.1). Median Lp(a) did not differ in beta blocker users (16 mg/dL) and in non-users (17 mg/dL), p greater than 0.1. Hypertensive, predominantly post-menopausal women are likely to have high plasminogen activator inhibitor activity and plasminogen activator inhibitor antigen with concurrent reduced fibrinolytic activity, as well as high fibrinogen levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein C and S deficiency, thrombophilia, and hypofibrinolysis: pathophysiologic causes of Legg-Perthes disease.

In eight patients with Legg-Perthes disease, we assessed the etiologic roles of thrombophilia caused by protein C and protein S deficiency and hypofibrinolysis mediated by low levels of tissue plasminogen activator activity. We speculated that thrombosis or hypofibrinolysis were common causes of Legg-Perthes disease. Three of the eight patients had protein C deficiency; they came from kindreds with previously undiagnosed protein C deficiency. In one of these three kindreds there were six protein C-deficient family members (beyond the proband child), four of whom had thrombotic events as adults. One of the eight patients had protein S deficiency, as did his brother who had sustained mesenteric vein thrombosis at age 43. One of the eight patients who had normal proteins C, S, and antithrombin III had hypofibrinolysis, failing to elevate tissue plasminogen activator activity after 10 min of venous occlusion at 100 mm Hg. Plasminogen activator inhibitor, alpha 2-antiplasmin, and fibrinogen values were normal in all eight patients. Beyond their Legg-Perthes disease, none of the eight patients had evidence for venous thrombosis. Of the eight patients, four had thrombophilia and one had hypofibrinolysis, disorders that we believe contributed to thrombotic venous occlusion of the femur with subsequent venous hypertension and bone death that characterize Legg-Perthes disease.

Hypofibrinolysis: a common, major cause of osteonecrosis.

In 30 patients with osteonecrosis of the hip (12 idiopathic, 18 secondary), we assessed the role of hypofibrinolysis mediated by high levels of plasminogen activator inhibitor (PAI). We evaluated hypofibrinolysis as a common, potentially reversible, pathophysiologic cause of idiopathic osteonecrosis. In all 18 patients with secondary osteonecrosis, PAI was normal, as was the ability to activate fibrinolysis. Nine of the 12 patients with idiopathic osteonecrosis had exceptionally high PAI levels and could not normally elevate tissue plasminogen activator (tPA-Fx), the major stimulator of fibrinolysis, after 10 min of venous occlusion at 100 mm Hg. The group of 12 patients with idiopathic osteonecrosis, compared to the 18 with secondary osteonecrosis, had low mean stimulated tPA-Fx (1.92 vs. 7.6 IU/ml, P < or = .001) and very high stimulated PAI-Fx (70 vs. 7.6 U/ml, P < or = .01). Three of the 12 patients with idiopathic osteonecrosis had both normal PAI and normal stimulated tPA-Fx. These three patients and 14 of the 18 with secondary osteonecrosis had high lipoprotein (a) [Lp(a)] (> 20 mg/dl). Mean Lp(a) was much higher (60 mg/dl) in the patients with secondary osteonecrosis than Lp(a) (16 mg/dl, P < or = .001) in the 12 patients with idiopathic osteonecrosis. These findings suggest that hypofibrinolysis mediated by high PAI is a common cause of idiopathic osteonecrosis, whereas high Lp(a) may play an etiologic role in secondary osteonecrosis. Prospective studies of patients with high PAI and/or high Lp(a) should be carried out to assess further their apparently causal roles in osteonecrosis.

Familial idiopathic osteonecrosis mediated by familial hypofibrinolysis with high levels of plasminogen activator inhibitor.

Familial hypofibrinolysis with 3 generation, autosomal dominant, very high levels of plasminogen activator inhibitor activity (PAI-Fx) and antigen (PAI-Ag) was etiologically associated with bilateral idiopathic osteonecrosis in 2 brothers. They, their mother, 2 brothers, sister, and all 4 of her children (none of whom had yet developed osteonecrosis), all had very high PAI and could not elevate tissue plasminogen activator after 10 minutes of venous occlusion at 100 mmHg. Familial high PAI levels with concurrent hypofibrinolysis co-segregated with familial combined hyperlipidemia, both being independent risk factors for premature coronary heart disease. If thrombi block venous drainage in the femur, familial hypofibrinolysis mediated by familial high PAI with inability to lyse thrombi would contribute to venous hypertension of bone, bone anoxia, and bone death characteristic of osteonecrosis.

Inheritance conjointly contributing to fibrinolysis and hyperlipidemia.

Our specific aim was to assess within-family relationships of basal fibrinolytic activity and its determinants in hyperlipidemic probands (n = 34) with high lipoprotein (a) [Lp(a)] levels (> 35 mg/dL) and their first-degree relatives (n = 74) and in hyperlipidemic probands (n = 19) with Lp(a) < 35 and their first-degree relatives (n = 23). Probands' plasminogen activator inhibitor activity (PAI-Fx), the major fibrinolysis inhibitor, correlated with first-degree relatives' PAI-Fx in high-Lp(a) kindreds (r = .30, P = .06) and in Lp(a) < 35 kindreds (r = .43, P < or = .05). Probands' tissue plasminogen activator activity (tPA-Fx), the major fibrinolysis activator, was inversely associated with first-degree relatives' PAI-Fx in high-Lp(a) kindreds (r = -.30, P = .06) and in Lp(a) < 35 kindreds (r = -.49, P < or = .025). These correlations [irrespective of probands' Lp(a)] pointed to within-family heritability of the major fibrinolysis inhibitor, PAI-Fx, and the fibrinolysis stimulator, tPA-Fx. There were many other within-family correlations. High-Lp(a) probands' tPA-Fx, the stimulator of fibrinolysis, correlated with first-degree relatives' tPA-Fx (r = .32, P < or = .05). High-Lp(a) probands' plasminogen was inversely correlated with first-degree relatives' alpha 2-antiplasmin, a major fibrinolytic inhibitor (r = -.41, P < or = .01), and with their Lp(a) [r = -.24, P < or = .05]. High-Lp(a) probands' tPA-Fx correlated inversely with first-degree relatives' apolipoprotein (apo) B (r = -.28) and triglyceride ([TG] r = -.41), and positively with their high-density lipoprotein cholesterol ([HDLC] r = .40) and apo A-1 (r = .33; all P < or = .025). High-Lp(a) probands' PAI-Fx correlated positively with first-degree relatives' apo B (r = .34) and TG (r = .47), and inversely with HDLC (r = -.34) and apo A-1 (r = -.30; all P < or = .01). By stepwise regression, the Quetelet index (a measure of relative ponderosity) was independently inversely associated with tPA-Fx (P < or = .05) and positively associated with tPA-Ag and PAI-Fx (P < or = .05). TG was a positive independent determinant of PAI-Fx (P < or = .05), alpha 2-antiplasmin (P < or = .05), and plasminogen (P < or = .05). Lp(a) was a positive, independent determinant of fibrinogen (P < or = .05).(ABSTRACT TRUNCATED AT 400 WORDS)

Endogenous testosterone, fibrinolysis, and coronary heart disease risk in hyperlipidemic men.

To assess relationships of endogenous testosterone with fibrinolysis and coronary heart disease risk factors in 55 newly referred hyperlipidemic men, we studied the relationships of testosterone to basal fibrinolytic activity, lipids, lipoproteins, and apolipoproteins. Testosterone correlated positively with the major stimulator of fibrinolysis, tissue plasminogen activator activity (r = 0.30; p = 0.02) and correlated inversely with two independent coronary heart disease risk factors, plasminogen activator inhibitor activity, the major fibrinolysis inhibitor (r = -0.33; p = 0.01), and fibrinogen (r = -0.39; p = 0.004). Testosterone correlated inversely with plasma triglycerides (r = -0.33; p = 0.01). Stepwise multiple regression was done with fibrinolytic activities as the dependent variables, and age, Quetelet Index (relative ponderosity), apolipoprotein A-I, apolipoprotein B, triglyceride, testosterone, time of blood sampling, and lipoprotein (a) as explanatory variables. Testosterone was an inverse, independent predictor of fibrinogen (p = 0.002); 53% of the variance of fibrinogen could be accounted for by age and triglyceride level (positive; p = 0.001, p = 0.01), and by apolipoprotein A-I and testosterone (negative; p = 0.02, p = 0.002). Testosterone was an independent inverse predictor of tissue plasminogen activator antigen (p = 0.0008), with tissue plasminogen activator antigen correlating inversely with tissue plasminogen activator activity. Quetelet index and apolipoprotein B were independent negative predictors of tissue plasminogen activator activity (p = 0.02, p = 0.03); Quetelet index and triglycerides were independent positive predictors of plasminogen activator inhibitor activity (p = .0001, p = .0001) and alpha 2-antiplasmin (p = 0.0003, p = 0.009).(ABSTRACT TRUNCATED AT 250 WORDS)

Familial high plasminogen activator inhibitor with hypofibrinolysis, a new pathophysiologic cause of osteonecrosis?

In a 29 year old white male with osteonecrosis of both hips and a shoulder, and in his family, we measured basal and stimulated (10 min cuff venous occlusion at 100 mgHg) fibrinolytic activity to determine whether low fibrinolytic activity might be heritable and etiologically associated with osteonecrosis. The proband's basal tPA-Fx was low, 0.08 IU/ml (normal 0.11-1.94), tPA-Ag was normal (11.6 ng/ml), plasminogen activator inhibitor activity (PAI-Fx) was very high, 119 U/ml (normal 3.5-27), as was his plasminogen activator inhibitor antigen (PAI-Ag), 202 ng/ml (normal 3.2-37.1). The proband's basal PAI-Fx (119) and PAI-Ag (202) were respectively 6 and 13 standard deviations greater than the mean PAI-Fx (17 +/- 15 U/ml) and the mean PAI-Ag (25 +/- 13 ng/ml) in 172 concomitantly studied hyperlipidemic men. Alpha-2 antiplasmin, fibrinogen, plasminogen and Lp(a) were normal. Despite lowering TG to 301 mg/dl, basal tPA-Fx remained low, 0.05; PAI-Fx and PAI-Ag remained very high (109 and 191). Following venous occlusion, stimulated tPA-Fx remained very low, 0.1 (normal 2.3-11.3), but tPA-Ag rose normally to 17 (normal 8.4-31.4); stimulated PAI-Fx and PAI-Ag were very high, 134 and 223, (normal PAI-Fx 3.6-24, PAI-Ag 12-96). Stimulated D-dimer was < the 10th percentile, 0.084 micrograms/ml. With such high PAI-Fx available to bind tPA, occlusion-stimulated tPA-Fx could not rise, and fibrinolysis could not be initiated. Neither diseases nor drugs could explain the high PAI-Fx and PAI-Ag, low tPA-Fx; or osteonecrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between lipoprotein(a), lipids, apolipoproteins, basal and stimulated fibrinolytic regulators, and D-dimer.

In 191 newly referred hyperlipidemic patients, our specific aim was to assess relationships between levels of lipoprotein(a) [Lp(a)], lipids, apolipoproteins, regulators of basal and stimulated fibrinolytic activity, and D-dimer, a measure of in vivo fibrinolysis. Lp(a) levels correlated with none of the measures of basal fibrinolytic regulators or D-dimer. In 25 patients, levels of stimulated regulators of fibrinolytic activity and D-dimer were measured after 10-minute cuff venous occlusion. Lp(a) levels again correlated with none of the stimulated regulators of fibrinolytic activity or D-dimer. However, both basal and stimulated levels of fibrinolytic regulators and D-dimer were closely related to other major risk factors for coronary heart disease (CHD) including triglyceride, apolipoprotein (apo) A1, apo B, Quetelet index (QI), and sex. By stepwise regression in 191 patients, the following standardized partial regression coefficients were significant (P < or = .05), and model R2 and P values were as follows: basal tissue plasminogen activator (tPA) with apo B-.18, with time .17, with QI -.28, R2 = 17%, P < or = .0001; basal plasminogen activator inhibitor (PAI) with apo B..25, with time -.15, with QI .17, R2 = 14%, P < or = .0001; basal alpha 2-antiplasmin with apo A1.14, with apo B.24, with QI.17, with sex .30, R2 = 25%, P < .0001; basal plasminogen with A1.15, with apo B.21, with QI.17, with sex.17, R2 = 15%, P < or = .0001; basal fibrinogen with Lp(a).17, with QI.21, with sex.26, R2 = 14%, P < or = .0001; D-dimer with sex.15, R2 = 21%, P < or = .048. Given the absence of any relationship between Lp(a) levels and inhibition or stimulation of fibrinolysis regulators or D-dimer either in the basal or stimulated state, we postulate that Lp(a)'s major atherogenic effects are mediated by mechanisms other than reduction of fibrinolysis stimulation or in vivo fibrinolysis.

Protein S deficiency and skin necrosis associated with continuous ambulatory peritoneal dialysis.

Skin necrosis associated with protein C deficiency has recently been reported to occur in hemodialysis patients. The clinical presentation and course of this syndrome appears indistinguishable from skin necrosis (purpura fulminans) seen in other settings with inherited or acquired deficiency of the naturally occurring anticoagulant proteins, protein C and S. Patients on maintenance hemodialysis may have low levels of these factors. However, patients on peritoneal dialysis have normal or elevated levels of these proteins despite documented peritoneal losses. We report two patients in whom the occurrence of protein S deficiency and subsequent skin necrosis can be related to demonstrated peritoneal dialysis-associated losses. We suggest that these losses may become critical under appropriate conditions and suggest caution in peritoneal dialysis patients requiring warfarin therapy.

The persistence and heterogeneity of factor VIII:C inhibitors as demonstrated by preparative isofocusing.

The purpose of this study was to determine if factor VIII:C inhibitors completely disappear during remission and if they recur on exacerbation, are they similar to or different from the original inhibitors? To answer these questions, isofocusing, which separates proteins on the basis of their pIs, was utilized to recover inhibitors from the plasmas of six patients, five nonhemophiliacs with acquired VIII:C inhibitors and the sixth with classic hemophilia. Initially, all plasmas were studied during the presenting hemorrhagic episodes and, subsequently, following the disappearance or recurrence of the inhibitors. Following isofocusing, each fraction was tested for inhibitory activity. The method enabled us to determine that inhibitors to factor VIII:C persisted even when they could not be demonstrated by conventional methods. The inhibitory activity resulted from a composite of inhibitors, each of the group identified by its own pI. In many patients, some peaks persisted throughout the entire interval of study, whereas others disappeared and new ones appeared, suggesting that various groups of cells were capable of producing the inhibitors.

Prenatal screening for anticardiolipin antibody.

Anticardiolipin antibodies, immunoglobulin G, and M (IgG, IgM) have been associated with recurrent abortion and with maternal death. This study tested whether anticardiolipin titers would be a useful prenatal screening test to determine high-risk pregnancies. Titers were obtained at the first clinic visit in 686 patients, mean gestation, 20 weeks. The outcome variables were taken from a medical records computer data base. IgG anticardiolipin correlated inversely with birthweight (p less than 0.025), but not with gestation. IgM anticardiolipin correlated strongly with the inverse of patient age (p less than 0.0002) and with chronic hypertension (p less than 0.01), but not with preeclampsia. There was a weak correlation with the 1-minute Apgar score (p less than 0.05). Thirty-seven patients had titers of IgG or IgM greater than 3 standard deviations above the mean for nonpregnant patients. Sixteen of these patients were studied for antinuclear antibody and coagulopathy (prothrombin time, partial thromboplastin time, viper venom time) and all were normal. Six of eight patients tested had low range elevated antibody titers to double-stranded DNA. Ten placentas were examined and showed no infarctions. None of the correlations were of practical clinical utility. The biologic basis of the correlations found is of further interest. The value of anticardiolipin titers with lupus erythematosus, or with coagulopathy, was not tested.

A monoclonal immunoglobulin A (kappa) factor VIII:C inhibitor associated with primary amyloidosis: identification and characterization.

Factor VIII:C inhibitors associated with primary amyloidosis have not been previously reported. A patient with autopsy-proved primary amyloidosis developed renal failure requiring peritoneal dialysis. Purpura and a prolonged partial thromboplastin time (PTT) were first observed 3 years later, after treatment was changed from peritoneal dialysis to hemodialysis. Plasma contained a time-dependent factor VIII:C inhibitor. The inhibitor on isoelectric focusing showed two peaks of activity, one with an isoelectric point (pl) of approximately 4 and the second larger, with a pl of approximately 8. Both were neutralized only by antisera to IgA and kappa light chain. A monoclonal antibody prepared in Balb/c mice against the variable region of the kappa light chain also blocked the inhibitor. The delayed onset of the coagulopathy could be explained by the change from peritoneal to hemodialysis, because in the former, significant amounts of the paraprotein, indicated by an "M-spike," were recovered in the dialysate. N-terminal amino acid sequencing of the first 20 amino acids of the variable region of the kappa light chain from the urinary protein and the splenic amyloid subunit showed identity.

The effects of argon laser on in vitro aggregation of platelets in platelet rich plasma and whole blood.

The effects of an Argon laser on platelet aggregation were studied, since platelets may be exposed to laser energy when used intravascularly. Various preparations of platelets in platelet rich plasma (PRP) and whole blood, with or without aspirin, were tested with the aggregating agents ADP, collagen, thrombin, and epinephrine. Simultaneous release of ATP was also measured in PRP. At relatively low levels of irradiation, platelet aggregation was potentiated. Enhancement was evidenced by an increase in percent aggregation, earlier onset of the reaction, and reduction in the amount of aggregating agent required. In PRP, the mechanism of laser potentiation appeared to be the release of endogenous ATP from platelets. At relatively high levels of irradiation, platelets were destroyed and aggregation abolished. In whole blood, the mechanism was somewhat more complicated since release of ATP occurred from RBCs as well as platelets. Spontaneous aggregation following laser treatment occurred in isolated instances in PRP and in every trial in whole blood preparations. Aspirin ingestion inhibited the laser's effects in PRP but not in whole blood. These results may have important clinical implications for laser angioplasty, and the potentiated aggregation response may prove useful in laboratory studies of platelet function.

An acquired inhibitor to factor VIIIC in a non-hemophiliac: twenty years of observation and characterization.

A non-hemophilic patient with an acquired inhibitor to factor VIIIC was initially diagnosed in this laboratory 20 years ago at age 63. Following its initial appearance in 1963, the inhibitor was detectable on two other occasions. We believe that this is the longest duration such an inhibitor has persisted. No sample remained from his initial admission; however, samples were available from the last 8 years of his life for retrospective study. Preparative isofocusing, affinity chromatography, and immunoglobulin subtyping were used to determine the similarities and/or differences in the inhibitor over these 8 years. The following similarities and differences were observed in both the 1975 and 1983 plasmas. Isofocusing showed that both plasmas contained peaks of inhibitory activity with pIs of 7.25, 8.26, and 8.88; the 1975 sample in addition contained two peaks with pIs of 7.77 and 9.45, whereas two other peaks with pIs of 7.64 and 7.85 were found in the 1983 sample. For the final characterization, each isofocused inhibitory peak was eluted from Protein A Sepharose and incubated with antisera to determine the immunoglobulin subtype. Each peak consisted of mixtures of IgG1 and IgG4 with both kappa and lambda light chains. It was concluded that the inhibitor was polyclonal, based on the presence of inhibitory peaks with different pIs and immunoglobulin subtypes. These findings support the conclusion that the development of and changes in the inhibitor was a dynamic process with some inhibitors (antibodies) persisting, while at the same time others with different characteristics were being formed.

Factor VIII inhibitors: in vivo decrease of inhibitory activity during calcium infusion.

The effect of parenteral calcium on altering the activity of factor VIII inhibitors has been studied in three patients, two nonhemophiliacs and one hemophiliac. The patients were studied during both intravenous calcium infusion, factor VIII replacement, and combinations thereof. When compared to factor VIII replacement alone, a greater diminution of inhibitory activity was noted whenever calcium was infused prior to and during factor VIII replacement. This was demonstrated by both conventional coagulation assays and an agarose gel method. These observations could have therapeutic implications and may aid in further understanding the relationship of calcium to factor VIII and its inhibitor.

Thrombosis in systemic lupus erythematosus. Relation to the presence of circulating anticoagulants.

In an earlier report on the kidney in systemic lupus erythematosus (SLE), we described a subset of patients with circulating anticoagulants; many had glomerular and arteriolar thrombosis in the absence of necrosis and subendothelial deposits. The present study extends these observations to a larger group of patients with SLE and a circulating anticoagulant, and compares its findings with those in patients with SLE without evidence of an anticoagulant. It demonstrates (1) a higher prevalence of clinically recognizable thrombotic events in the venous and arterial circulations in patients with SLE and a detectable anticoagulant; (2) a probable shortening in life span; (3) a higher prevalence of glomerular thrombi; (4) elevated levels of factor VIII antigen and von Willebrand factor; and (5) significantly lower platelet counts and decreased in vitro platelet aggregation in response to adenosine diphosphate, epinephrine, and collagen. Since prednisone treatment often results in improvement or disappearance of a prolonged partial thromboplastin time, the test most commonly used for screening of a circulating anticoagulant, we suggest that the prevalence of this abnormality may be underestimated in patients with SLE.

Agarose gel method: its usefulness in assaying factor VIII inhibitors, evaluating treatment and suggesting a mechanism of action for factor IX concentrates.

Plasmas from 14 patients with factor VIII inhibitors, 10 haemophiliacs and four non-haemophiliacs, were assayed by both the agarose gel and Bethesda methods. Good correlation was observed in 34 samples from 13 patients, but there was poor correlation in three samples from a single haemophilic patient. The sensitivity of the method was increased by diluting normal platelet rich plasma (PRP) with congenital factor VIII deficient plasma. With this modification, as little as 0.4 of a Bethesda unit (Bu) could be measured accurately. The agarose method is easier to perform and requires much less technician time than the Bethesda assay (Ba). Inhibitory activity can be measured even in the presence of large amounts of transfused factor VIII or factor IX concentrates. To study the effect of factor IX concentrates on the inhibitor, the method was modified by incorporating into the gels plasmas specifically deficient in either factor VII, IX or X. Our data suggest that factor VII is probably responsible for the 'bypassing' activity of factor IX concentrates.