The Standard Point-of-Care Hemochron Jr. ACT+ Test in Monitoring Heparin Administration for Cardiopulmonary Bypass in Severe Factor XII Deficiency.

Coagulation factor XII (FXII) is a plasma serine protease that belongs to the contact activation complex responsible for initiating the intrinsic coagulation pathway. FXII deficiency is a rare congenital disorder that is not associated with an increased tendency for bleeding. However, as contact activation is impaired in FXII deficiency, both the celite- and kaolin-initiated activated clotting time (ACT) measurements are prolonged markedly, which poses a challenge for anticoagulation monitoring in patients undergoing cardiac surgery. The authors successfully have used the standard Hemochron Jr. ACT+ test, which is activated by silica and phospholipid in addition to kaolin, to monitor anticoagulation for cardiopulmonary bypass in two patients with severe FXII deficiency. The ACT+ test showed low baseline values, increased adequately in response to heparin, and decreased to baseline after protamine. Importantly, there was no abnormal intra- or postoperative bleeding nor any thrombotic complications. Furthermore, in vitro dose-response ACT+ testing of FXII-deficient blood with increasing heparin concentrations supports the use of ACT+ in FXII deficiency.

Acquired factor XII deficiency following transanal excision of rectal lesion by transanal minimally invasive surgery (TAMIS): a case report and literature review.

BACKGROUND: Local excision (LE) is currently one of the most effective methods used in cases of large benign polyps, not suitable for endoscopic treatment, or early-stage neoplasms. LE is also alternative to anterior rectal resection in selected patients suffering from major comorbidities and limits for major abdominal procedure. Furthermore, LE results in less pain, reduced impact on bowel function, shorter duration of hospital stay, and lower rates of morbidity, mortality and stoma creation. In particular, early data on transanal minimally invasive surgery (TAMIS) are promising, but they come from single centre case series related to small groups of patients and more data are needed to draw a final conclusion on the safety of this novel approach for transanal resection. CASE PRESENTATION: A 62-year-old woman, following a positive faecal occult blood test and with unremarkable medical history, was admitted to hospital for excision of a large flat neoplastic lesion. Endoscopic biopsy demonstrated a tubular adenoma with high-grade dysplasia and was decided to proceed with surgical excision by TAMIS. After surgery, short-term outcomes revealed prolonged activated partial thromboplastin time, undetectable factor XII activity, fever, and partial dehiscence of rectal wall defect suture. Cross-mixing studies of patient plasma show no correction in either the immediate or incubated activated partial thromboplastin time, indicating the presence of an acquired factor XII inhibitor. Activated partial thromboplastin time and factor XII improved in the following weeks without any specific therapy in addition to antibiotic therapy. CONCLUSION: This is the first report in which acquired inhibitor of coagulation factor XII is associated with a specific surgical procedure. This case has shown how trans-anal excision of rectal lesions, even when performed by minimally invasive means such as in case of TAMIS, is not free of complications. We consider the acute infection, resulting from early dehiscence of the suture, the trigger in an abnormal immune response, and inhibitor development.

[Are we to pay attention to factor XII deficiency?]. / Máme venovat' pozornost' defektu koagulacného faktora XII?

Severe coagulation factor XII (FXII) deficiency is a very rare, mysterious and not well known inherited condition. Unlike other coagulation factor deficiencies, it is totally asymptomatic. Surprisingly, it does not lead to abnormal bleeding, even with major surgical procedures. The explanation for the lack of bleeding manifestations is unknown. It is suggested, but unproven, that patients are not sufficiently protected from thrombosis. FXII deficiency is usually discovered by accident through a routine coagulation testing done prior to surgery. Since FXII plays an important role in clot formation during in vitro measurements, its deficiency causes a marked prolongation of the activated partial thromboplastin time in the laboratory examination. The main concern related to FXII deficiency is the unnecessary testing, delay in health care and worry of surgical interventions that may be prompted by the abnormal laboratory result.

[Identification of a novel mutation of factor XII gene in a family with coagulation FXII deficiency].

OBJECTIVE: To analyze genetic mutation and molecular pathogenesis in a family affected with inherited coagulation factor XII(FXII) deficiency. METHODS: Activated partial thromboplastin time (APTT), FXII procoagulant activity (FXII:C), FXII antigen (FXII:Ag) and other coagulants were measured. For affected members of the family, exons 1-14 and flanking intronic regions of the FXII gene were amplified with polymerase chain reaction (PCR) and sequenced thereafter. Expression plasmids containing mutant FXII cDNA was constructed and transfected into COS7 cells transiently. Expressions of FXII:Ag and FXII:C were analyzed. RESULTS: The proband has manifested a prolonged APTT of 108.1 s (reference range: 27.0-41.0 s). Her husband has a normal APTT. Other members of the family had slightly increased APTT. The FXII:C and FXII:Ag of the proband have both dropped to about 0.01 (reference range: 0.72-1.13). The FXII:C levels of her husband, son, daughter and grandchild were 0.57, 0.24, 0.14, 0.16, respectively. And the FXII:Ag levels in her husband, son, daughter and grandchild were 0.55, 0.27, 0.15, 0.21, respectively. The proband and her daughter have both carried a heterozygous deletional mutation 6800-6808delAGCTGGGAG (6800-6808del9bp) in exon 9. For the promoter region of the FXII gene, the genotypes of the proband, her son, daughter and grandchild was TT, whilst that of her husband was CT. Expression study has shown that, whilst the mutant FXII protein has accumulated in the cells similar to wild-type protein, its secretion has reduced approximately by half. CONCLUSION: A novel deletional mutation 6800-6808del9bp has been identified in the FXII gene. Although mutant FXII protein can still accumulate in cells, its secretion has become insufficient. The 6800-6808del9bp mutation and 46T/T have both contributed to the pathogenesis of FXII deficiency in the family, but may have not been the sole cause.

A Novel Homozygous Missense Mutation (Ile583Asn) in a Consanguineous Marriage Family with Hereditary Factor XII Deficiency: A Case Report.

BACKGROUND: Hereditary coagulation factor XII (FXII) deficiency is an autosomal recessive disorder. At present, the contribution of severe FXII deficiency to the development of thromboembolism is still undetermined. There are limited reports on the relationship between the FXII defect and thromboembolism. CASE PRESENTATION: A 27-year-old woman came to our hospital for the treatment of shoulder trauma and cervical disc herniation caused by a car accident. The shoulder trauma was treated with five stitches. After physical examination, imaging examination, and routine coagulation examination, cervical disc herniation was treated conservatively. Combined with the examination results, the patient was diagnosed with FXII deficiency. Unfortunately, the patient was readmitted 10 days after the trauma with edema in the lower limbs and secondary varicose veins. The D-dimer increased to 6.22 mg/L. Thrombus in the inferior vena cava and right common iliac was shown by lower limb venography. According to the patient's medical history, the F12 gene was analyzed by direct sequencing. The patient was also screened for other thrombotic risk factors. Genetic analysis showed that the patient had a c.1748T > A (p.Ile583Asn) homozygous missense mutation in exon 14 of the F12 gene. No other hereditary thrombophilia risk factors screened were positive in the patient. CONCLUSION: The p.Ile583Asn missense mutation in exon 14 of the F12 gene might be responsible for the reduction of the FXII level in the patient.

An unanticipated prolonged baseline ACT during cardiac surgery due to factor XII deficiency.

Factor XII (FXII) deficiency is a congenital disorder inherited as an autosomal recessive condition. In his heterozygous form, it is relatively common in the general population. However, a total absence of FXII as seen in homozygous patients, is rare, with an incidence of approximately 1/1,000,000 individuals. Surprisingly, FXII deficiency is rather associated with thromboembolic complications. Patients do not experience a higher risk of surgical bleeding despite a markedly prolonged activated partial thromboplastin time. Given its low incidence in the general population, the finding of an unknown FXII deficiency is rare during cardiac surgery. This unique case describes a patient with an unanticipated prolonged baseline activated clotting time (ACT) during cardiac surgery in which his bleeding history and rotational thromboelastometry tracings lead us to the diagnosis of a FXII deficiency. The finding of a hypocoagulable INTEM tracing and a concurrent normal EXTEM tracing in a sample of a patient with prolonged ACT and adverse anamnestic bleeding history should prompt clinicians to consider a FXII deficiency. It may help clinicians in further perioperative management where there is not enough time to wait for the results of individual coagulation factor testing.

Report 2 cases of congenital factor XII deficiency: a rare coagulation disorder.

Factor XII (F.XII, Hageman factor) is one of the contact system factors which initiates an intrinsic coagulation pathway. But its definite role is still unclear, because many cases of severe F.XII deficiency experience thrombotic events instead of a bleeding problem. Moreover most of them are asymptomatic. There have only been a few reports of F.XII deficiency in Thailand. The author reports two cases of congenital F.XII deficiency in Thai children.

Congenital hemophilia A with low activity of factor XII: a case report and literature review.

BACKGROUND: Congenital hemophilia A is a recessive inherited hemorrhagic disorder. According to the activity of functional coagulation factors, the severity of hemophilia A is divided into three levels: mild, moderate and severe. The first bleeding episode in severe and moderate congenital hemophilia A occurs mostly in early childhood and mainly involves soft tissue and joint bleeds. At present, there are limited reports on severe congenital hemophilia A with low factor XII (FXII) activity during the neonatal period. CASE PRESENTATION: A 13-day-old neonate was admitted to the hospital with hematoma near the joints of both upper arms. Coagulation tests showed he had low activity of factor VIII (FVIII) and FXII. He was diagnosed with congenital hemophilia A and treated with human coagulation factor VIII (recombinant FVIII). Although the hematoma became smaller, FVIII activity was only increased to a certain extent and FXII activity decreased gradually. Unfortunately, the child responded poorly to recombinant human coagulation factor VIII and his guardian rejected prophylactic inhibitors and genetic testing and refused further treatment. Three months later, the child developed intracranial hemorrhage (ICH) due to low FVIII activity. CONCLUSIONS: In hemophilia A, the presence of FVIII inhibitors, drug concentration and testing are three important aspects that must be considered when FVIII activity does not reach the desired level. Early positive disease treatment and prophylaxis can decrease the frequency of bleeding and improve quality of life. We recommend that pregnant women with a family history of hemophilia A undergo early prenatal and neonatal genetic testing.

Enhanced cortical reperfusion protects coagulation factor XII-deficient mice from ischemic stroke as revealed by high-field MRI.

Intrinsic coagulation factor XII deficient (FXII(-/-)) mice are protected from ischemic stroke. To elucidate underlying mechanisms we investigated the early ischemic period in vivo by multimodal magnetic resonance imaging (MRI) at 17.6 Tesla. Cerebral ischemia was induced by either transient (60 min) or permanent occlusion of the middle cerebral artery (t/pMCAO). 10 FXII(-/-) mice underwent t- , 10 FXII(-/-) mice p- and 10 Wildtype (Wt) mice tMCAO. Cerebral blood flow (CBF), diffusion-weighted-imaging (DWI) and T2-relaxometry were measured at 2 h and 24 h after MCAO. Outcome measures were evaluated after motion correction and normalization to atlas space. 2 h after tMCAO CBF reduction was similar in FXII(-/-) and Wt mice extending over cortical (CBF (ml/100 g/min) 33.6+/-6.9 vs. 35.3+/-4.6, p=0.42) and subcortical regions (25.7+/-4.5 vs. 31.6+/-4.0, p=0.17). At 24 h, recovery of cortical CBF by +36% was observed only in tMCAO FXII(-/-) mice contrasting a further decrease of -30% in Wt mice after tMCAO (p=0.02, F((1,18))=6.24). In FXII(-/-) mice in which patency of the MCA was not restored (pMCAO) a further decrease of -75% was observed. Cortical reperfusion in tMCAO FXII(-/-) mice was related to a lower risk of infarction of 59% vs. 93% in Wt mice (p=0.04). Subcortical CBF was similarly decreased in both tMCAO groups (Wt and FXII(-/-)) relating to a similar risk of infarction of 89% (Wt) vs. 99% (FXII(-/-), p=0.17). Deficiency of FXII allows neocortical reperfusion after tMCAO and rescues brain tissue by this mechanism. This study supports the concept of FXII as a promising new target for stroke prevention and therapy.

A novel homozygous missense mutation (Met527Ile) in a consanguineous marriage family with inherited factor XII deficiency.

OBJECTIVE: To identify potential mutations of the FXII gene (F12) in a consanguineous marriage family with hereditary coagulation factor XII (FXII) deficiency, and it will improve the understanding of the pathogenesis involved in the disease. CLINICAL PRESENTATION: The proband was a 58-year-old male who had chronic gastritis. He was found to have a significantly prolonged activated partial thromboplastin time (APTT) at 101.0s (reference range, 29.0-43.0 s) before stomachendoscopy. TECHNIQUES: The coagulation factor XII activity (FXII:C) and FXII antigen (FXII:Ag) were measured by one-stage clotting assay and enzyme-linked immunosorbent assay, respectively. The F12 gene was amplified by polymerase chain reaction and sequenced. Mutation sites were further confirmed by reverse sequencing. The conservatism and possible impact of the amino acid substitution were analyzed by multiple bioinformatics tools, as well as 3D protein model analysis. RESULTS: The proband had a prolonged APTT (101.0 s), whose FXII:C and FXII:Ag were obviously reduced, both at 1.0% (normal range, 72-113%). Gene sequencing revealed that he carried a homozygous missense mutation of Met527Ile. Family study showed that his mother, son and daughter carried a heterozygous Met527Ile. Bioinformatics and model analysis of the mutation indicated that Met527Ile may be detrimental and potentially alters the structure and the function of the protein. CONCLUSION: The novel mutation Met527Ile could potentially account for the reduced activity of FXII in this family.

Monitoring thrombin generation: is addition of corn trypsin inhibitor needed?

Thrombin generation monitoring has the potential to be used as a clinical diagnostic tool in the near future. However, robust preanalytical conditions may be required, and one factor that has been reported is in-vitro contact activation that might influence in-vitro measurements of thrombin generation and thereby act as an unpredictable pre-analytical variable. The aim of the current study was to investigate the influence of contact activation and the necessity of corn trypsin inhibitor (CTI) to abolish contact activation in thrombin generation measurements at low tissue factor (TF) concentrations. Thrombin generation was performed using the calibrated automated thrombinoscopy (CAT), thereby determining the endogenous thrombin potential (ETP), peak height, and the lag time, in plasma obtained from healthy volunteers. Addition of CTI after plasma preparation had no significant influence on thrombin generation triggered with 0.5 pM TF or higher, as demonstrated by unaltered ETP and lag time values between analyses with and without CTI. Addition of CTI before blood collection reduced thrombin generation triggered with 0.5 pM TF: both the ETP and peak height were significantly reduced compared to no CTI addition. In contrast, thrombin generation remained unaltered at a 1 pM TF trigger or above. This study demonstrates that addition of CTI after plasma separation is not necessary when triggering with TF concentrations of 0.5 pM and higher. Furthermore, it was demonstrated that it is not needed to pre-fill blood collecting tubes with CTI when measuring thrombin generation at TF concentrations of >/=1 pM.

Contact factor deficiencies and cardiopulmonary bypass surgery: detection of the defect and monitoring of heparin.

Contact factor pathway deficiencies do not cause surgical bleeding but make heparin monitoring by the activated partial thromboplastin time (APTT) and activated clotting time (ACT) unreliable. Heparin monitoring during cardiopulmonary bypass (CPB) surgery in these patients is particularly challenging. Here we describe heparin monitoring during CPB using the chromogenic anti Xa assay in two patients with severe factor XII deficiency (FXII < 0.01 U/mL) and one patient with severe prekallikrein (PK) deficiency (PK < 0.01 U/mL). Anti Xa levels of the three patients during CPB varied between 3.8 and 4.8 U/mL in keeping with a control group (mean anti Xa 4.5 U/mL and ACT > 480 s). There were no bleeding or thrombotic complications. We also found that detection of severe PK deficiency by the APTT in the PK deficient patient was dependent on the reagent used and discuss the sensitivity of different APTT reagents for contact factor deficiencies. We conclude that the sensitivity of APTT methods for contact pathway deficiencies is highly variable and although insensitivity is not a clinical problem in terms of bleeding, it can be a cause of discrepancy between different APTT reagents and the ACT. This can lead to confusion about a possible haemorrhagic tendency and delays in surgery. If these patients need to undergo cardiac surgery requiring high dose heparin treatment, monitoring by chromogenic anti Xa assay is a good alternative.

Deep venous thrombosis and previous myocardial infarction in mild factor XII deficiency: a risk factor for both venous and arterial thrombosis.

Factor XII deficiency is associated with increased risk for both arterial and venous thrombosis. We describe a case of DVT involving superficial femoral and popliteal vein occurred following total hip replacement and despite prophylaxis with low molecular weight heparin in a subject with previous acute myocardial infarction (AMI). Tests of haemostasis documented a slightly prolonged activated partial thromboplastin time (APTT) (45'') due to mild factor XII deficiency (clotting activity 32%). A therapeutic dose of enoxaparin was started, together with warfarin therapy. The patient was advised to continue oral anticoagulation indefinitely. Although cases of both venous and arterial thrombosis in carriers of severe factor XII deficiency have been already reported, to our knowledge this is the first case in the literature occurred in a carrier of partial factor XII deficiency. In conclusion, factor XII deficiency should be suspected if a patient presents with recurrent arterial and/or venous thrombosis and prolonged APTT. If this defect is diagnosed, in the presence of a history of thrombotic events, lifelong anticoagulation could be considered.

Factor XII (Hageman Factor) Deficiency: a rare harbinger of life threatening complications.

Hageman factor (factor XII) has a key role in activation of intrinsic coagulation system gauged by activated partial thromboplastin time (aPPT). Hageman factor deficiency is more often an autosomal recessive condition, but an autosomal dominant inheritance is also reported. This condition in its own is not known to cause bleeding complications rather is associated with paradoxical fatal thromboembolic complications. Exact prevalence of this condition is not known, as under normal conditions they are asymptomatic. In literature, a prevalence of 2.3% has been reported in one study on 300 patients presenting with complications. Homozygous patients has non-detectable levels of factor XII, while heterozygous individuals has variable levels ranging from 20-60%. Hageman factor is a pro-coagulation protein initiating intrinsic pathway. Intrinsic pathway is activated either by direct contact with a negative charged surface or by proteolytic activation on the endothelial cells via prekallikerin/kallikerin system. Factor XII as an integral part of this system leads to factor XI activation resulting in production of thrombin orchestrated by intrinsic system. In addition, there is concomitant activation of complement components C3 and C5 via C1-estrase activation. Patients with this condition are known to have spontaneous thromboembolic complications although less common but are prone to life threatening complications under provocating circumstances. The aim of this case report is to study the relation of factor XII deficiency and isolated raised activated partial thromboplastin time (aPPT) and how it can be prevented. We are presenting a Saudi female patient, 29 years of age who presented to accident and emergency room (A&E room) of our hospital with sudden severe breathlessness and chest pain.

Factor XIII deficiency in children--clinical presentation and outcome.

OBJECTIVE: To determine the demographic features and clinical outcome of children with Factor XIII deficiency. STUDY DESIGN: Observational case series. PLACE AND DURATION OF STUDY: The Aga Khan University Hospital, Karachi, from January 1996 to December 2006. METHODOLOGY: Records of all hospitalized pediatric patients with discharge diagnosis of FXIII D, on the basis of factor XIII assay 5 mol/L urea test were retrospectively reviewed and abstracted on a pre-specified proforma. Demographic features, coagulation profile, family history and outcomes were noted. RESULTS: A total of 10 charts were reviewed. There were 5 boys and 5 girls. Almost all the children (9/10) were less than 5 years of age, out of whom 5 (50%) were infants, and 3 were neonates. Bruises and prolonged bleeding after trauma was the major presenting complaints in 80%, followed by prolonged bleeding from the umbilical stump in 2 patients. Nine patients had past history of prolonged umbilical bleeding. Two patients had history of FXIII D in siblings, while 2 had history of prolonged bleeding in other family members (cause unknown). Consanguinity was present in 80% of the families. Initial coagulation screen were normal in all patients. Two patients had intracranial hemorrhage, proved on neuro-imaging, were managed with plasma infusions and required craniotomy. The rest were managed conservatively with plasma transfusions. All were discharged alive in good clinical condition. Almost all were followed regularly in clinic with monthly cryoprecipitate transfusions. CONCLUSION: Although factor XIII deficiency is a rare genetic disorder in children with history of bruising, prolonged umbilical bleeding, family history of bleeding and consanguinity with normal initial coagulation screen (PT, APTT and platelets), FXIII D should be ruled out.

Lemierre's syndrome complicating bacterial pharyngitis in a patient with undiagnosed factor XII deficiency.

Internal jugular vein thrombosis occurs as an uncommon complication of oropharyngitis. The following case report describes a previously healthy adult woman who presented with sore throat, left ear pain, and fever. She was initially diagnosed with pharyngitis and inadvertently had blood cultures sent as part of her workup. She was then called back to the Emergency Department the following day for positive growth of the blood culture, and found to have thrombophlebitis of the internal jugular vein on computed tomography scan of the neck. Further workup revealed factor XII deficiency. The clinical course was further complicated by septic pulmonary emboli and disseminated intravascular coagulation. The patient was treated with broad-spectrum antibiotics and anticoagulation and made a full recovery.

[Review of patients studied for coagulopathy in a Hematology/Oncology unit]. / Revisión de los pacientes estudiados por coagulopatía en una unidad de Oncohematología.

INTRODUCTION: Symptoms/signs suggestive of coagulopathy is a frequent complaint in Pediatric Hematology units. Both the clinical and family history are essential for diagnosis. PATIENTS AND METHODS: Retrospective and descriptive study of patients referred to a Pediatric Hematology unit of a tertiary hospital for possible coagulopathy during 2012. RESULTS: A total of 47 children were studied, of whom 61.7% had not previously suffered bleeding. The most frequent reason for referral was an eloganted activated partial thromboplastin time without any hemorrhage (42.5%), of these, 25% were diagnosed of a coagulopathy with a real risk of bleeding. While patients referred due to an eloganted activated partial thromboplastin time with bleeding more frequently (41.7%) have a coagulopathy with a real risk of bleeding. Children with a family history of bleeding are diagnosed more frequently with a coagulopathy with a real risk of bleeding: 37.5% (family history) vs. 14.3% (without). The most frequent diagnoses were: healthy children (48.9%), von Willebrand type 1 disease (19.1%), factor xii deficiency (19.1%), factor xi deficiency (4.2%), prekalikrein/high molecular weight kininogen deficiency (2.1%), acquired deficiency of factor x (2.1%), and factor ix deficiency (2.1%). CONCLUSIONS: A thorough personal and family bleeding history and physical examination are the first steps for a correct differential diagnosis. The reason for referral should be based more on clinical bleeding and not just on an abnormal coagulation time. The most frequent diagnoses were type 1 von Willebrand disease and factor xii deficiency.

Low levels of plasma protein S, protein C and coagulation factor XII during early pregnancy and adverse pregnancy outcome.

It was the study objective to evaluate whether low levels of plasma protein S (PS) activity, free PS, protein C (PC) activity and coagulation factor XII (FXII) during early pregnancy are related to adverse pregnancy outcomes. Peripheral blood samples were obtained at 8-14 gestational weeks (GW) from a consecutive series of 1,220 women. The levels of plasma PS activity, free PS, PC activity, and FXII were measured. Cut-off values were defined as < 1st, < 5th, and < 10th percentiles of values obtained from 933 women whose pregnancies ended in normal deliveries without complications. PS activity of < 10th percentile yielded risks of pregnancy-induced hypertension (PIH) and severe PIH, while free PS level of < 5th percentile yielded a risk of pre-eclampsia. FXII level of < 1st percentile yielded a risk of premature delivery (PD) at < 34 GW. None was associated with PD at < 37 GW, fetal growth restriction or fetal loss. A multivariate analysis demonstrated that PS activity of < 10th percentile (odds ratio 5.9, 95 % confidence interval 1.7-18.1) and body mass index (BMI) ≥ 25 kg/m² (4.3, 1.1-13.3) were independent risk factors for severe PIH. Similarly, free PS level of < 5th percentile (4.4, 1.0-14.3) and BMI ≥ 25 kg/m² (4.0, 1.3-10.9) were independent risk factors for pre-eclampsia. In conclusion, women with low levels of plasma PS activity and free PS during early pregnancy might have increased risks of PIH, severe PIH or pre-eclampsia. Women with low FXII level might have an increased risk of PD at < 34 GW.

Factor XII and other hemostatic protein abnormalities in nephrotic syndrome patients.

Factor XII clotting activities and antigen levels were assayed in 14 plasma samples from 10 patients with nephrotic syndrome; the group was heterogeneous clinically and histologically. Factor XII was low at initial sampling in 7 of the 10 patients; in 7 of the 14 samples, factor XII antigen was in excess over clotting activity. Inhibition of factor XII could not be demonstrated; excess plasma antigen and urinary antigen (when present) had normal patterns on crossed-immunoelectrophoresis, indicating no major changes in charge or size. In 3 patients tested more than once, plasma levels of factor XII were increased up to 6fold in steroid-induced remission. Of other hemostatic factors assessed for comparison, factor VIII was elevated in 11 of the 14 samples; eight of these had elevated factor VII levels as well. Eight samples from six patients showed low antithrombin III levels; one of these patients had recurrent thromboses. Antithrombin III levels correlated with the serum albumin concentration. Only two of the eight urines tested had detectable factor XII antigen; a third had factor IX and prothrombin and no factor XII. Plasminogen and antithrombin III were readily demonstrated in all urine samples with higher concentrations in those patients with less selective proteinuria. Urinary and plasma levels were not correlated, suggesting that increased consumption or turnover was not simply related to increased filtration.

Assay of Factor XII clotting activity in heparinized plasma.

Clotting tests based upon the activated partial thromboplastin time are disturbed by heparin. This brief communication shows that Factor XII clotting activity in plasma samples heparinized in vitro and in vivo can be measured accurately by means of an aPTT-test using congenitally deficient substrate plasma when the plasma dilution buffer contains hexadimethrine bromide (Polybrene), 15 mg/L. This method of neutralizing heparin obviates more complicated procedures such as heparin adsorption to anion exchange resins.