Kaija Javela

Fetal intracranial haemorrhages caused by fetal and neonatal alloimmune thrombocytopenia: an observational cohort study of 43 cases from an international multicentre registry

Objective To characterise pregnancies where the fetus or neonate was diagnosed with fetal and neonatal alloimmune thrombocytopenia (FNAIT) and suffered from intracranial haemorrhage (ICH), with special focus on time of bleeding onset. Design Observational cohort study of all recorded cases of ICH caused by FNAIT from the international No IntraCranial Haemorrhage (NOICH) registry during the period 2001–2010. Setting 13 tertiary referral centres from nine countries across the world. Participants 37 mothers and 43 children of FNAIT pregnancies complicated by fetal or neonatal ICH identified from the NOICH registry was included if FNAIT diagnosis and ICH was confirmed. Primary and secondary outcome measures Gestational age at onset of ICH, type of ICH and clinical outcome of ICH were the primary outcome measures. General maternal and neonatal characteristics of pregnancies complicated by fetal/neonatal ICH were secondary outcome measures. Results From a total of 592 FNAIT cases in the registry, 43 confirmed cases of ICH due to FNAIT were included in the study. The majority of bleedings (23/43, 54%) occurred before 28 gestational weeks and often affected the first born child (27/43, 63%). One-third (35%) of the children died within 4 days after delivery. 23 (53%) children survived with severe neurological disabilities and only 5 (12%) were alive and well at time of discharge. Antenatal treatment was not given in most (91%) cases of fetal/neonatal ICH. Conclusions ICH caused by FNAIT often occurs during second trimester and the clinical outcome is poor. In order to prevent ICH caused by FNAIT, at-risk pregnancies must be identified and prevention and/or interventions should start early in the second trimester.

Persistent antiphospholipid antibody (aPL) in asymptomatic carriers as a risk factor for future thrombotic events: a nationwide prospective study

Objectives The long-term prognosis of individuals fulfilling the laboratory criteria, but not clinical criteria, of antiphospholipid syndrome (APS) has not been widely investigated. The primary aim of this study was to evaluate the incidence of first thrombotic event (deep venous thrombosis (DVT), pulmonary embolism (PE), myocardial infarction (MI), stroke or transient ischaemic attack (TIA) in a nationwide antiphospholipid antibody (aPL) carrier cohort. Design We conducted a prospective nationwide cohort study. Setting The aPL profile of participants was recorded from the laboratory database. Information was collected about thrombotic and pregnancy complications, subsequent medical history, other risk factors for thrombosis, use of prophylactic antithrombotic medication and general health. Participants Participants included adult asymptomatic aPL carriers recognized in Finland during 1971–2009. Main outcome measure The main outcome measure was incidence of first thrombotic event. Results A total of 119 (89% female) aPL carriers were followed for mean (SD) of 9.1 (7.5) years (range 3–41 years). Sixty-one per cent of the study participants had autoimmune disease, most often systemic lupus erythematosus (SLE). Thirty-six of 119 (30%) were either double or triple positive, 56% single lupus anticoagulant (LA) positive, and 8% and 5% single anticardiolipin antibodies (aCL) and anti-β2glycoprotein I antibodies (aβ2GPI) positive, respectively. Nine (7.6%) study patients experienced a first thrombotic event (five DVT, one PE, two MI, one TIA) mean (SD) 7.2 (8.3) years (range 1–26 years) after aPL detection (annual incidence rate 0.8%). All individuals who developed thrombotic complications had autoimmune disease. Annual rate of first thrombotic event in carriers of single positivity (0.65%) was equal to the known risk of thrombosis in the healthy Caucasian population, whereas the rate was two times higher in carriers of double or triple positivity (1.27%). Sixteen of 79 (20%) women experienced pregnancy complications. Conclusions Double or triple positivity for aPL is a risk factor for future thrombotic events, especially in individuals with an underlying autoimmune disease, whereas single positivity does not seem to carry an elevated risk of thrombosis.

Variant Bernard-Soulier syndrome due to homozygous Asn45Ser mutation in the platelet glycoprotein (GP) IX in seven patients of five unrelated Finnish families.

Abstract:  Bernard‐Soulier syndrome (BSS), a rare bleeding disorder with macrothrombocytopenia, is caused by a defect of the platelet glycoprotein (GP) Ib/IX/V complex. Here we report a variant form of BSS in eleven patients of five unrelated families who originate from a particular area of Finland. The differential diagnosis from idiopathic thrombocytopenic purpura was difficult. Bleeding symptoms were epistaxis and haematomas debuting in childhood, but no spontaneous, severe bleeding episodes were reported. The platelet count varied from 43 to 81 × 109/l. Screening the entire GP Ibα, GP Ibβ, GP IX and GP V genes revealed a recurrent homozygous Asn45Ser mutation in GP IX in all probands. Flow cytometry showed markedly reduced expression of GP Ib (<10%), and only moderately reduced expression of GP IX (24–36%) and GP V (38–49%). The expression of subunits seemed to vary independently from the normal polymorphisms. Heterozygotes did not differ significantly from controls by their GP Ib/IX/V expression. Since the Asn45Ser mutation has also been reported in three other kindreds of northern and central European origin, this study reveals that instead of being a mutation hot spot, it may be ancient and scattered in Europe. Moderate, chronic thrombocytopenia should be carefully studied to diagnose variant BSS correctly from treatment resistant idiopathic thrombocytopenia.

Alloantibodies against low-frequency human platelet antigens do not account for a significant proportion of cases of fetomaternal alloimmune thrombocytopenia: evidence from 1054 cases

BACKGROUND: Maternal alloantibodies against the five common human platelet antigen (HPA) systems (HPA‐1 to ‐3, ‐5, and ‐15) are found in only 20% of cases referred for fetal and neonatal thrombocytopenia (FMAIT) investigations. The question asked was whether mismatches for the remaining 11 low‐frequency HPAs (HPA‐4 and ‐6bw to ‐17bw) might in part explain the remaining 80% of cases.

Type II antithrombin deficiency caused by a founder mutation Pro73Leu in the Finnish population: clinical picture

It has been shown that some antithrombin (AT) activity assays do not correctly detect inherited type II AT deficiency, but erroneously classify these patients as normal.

Chronic thrombocytopenia of childhood: use of non-invasive methods in clinical evaluation.

Objectives : An unselected group of 21 children with chronic thrombocytopenia was investigated to understand the patients’ platelet abnormality better.

Detection of reticulated platelets: estimating the degree of fluorescence of platelets stained with thiazole orange.

Abstract: The primary problem in the measurement of reticulated platelets (RP) stained with thiazole orange (TO) by flow cytometry is the definition of a threshold limit for fluorescence positivity. We evaluated settings for the threshold gate for TO positivity based on two principles: a fluorescence histogram (median FL1, Relative FL1) or a plot of forward light scatter (FSC; reflecting the distribution of the platelet size) versus fluorescence intensity (% RP). These methods were applied prospectively in examination of 54 healthy blood donors (16 females) and a total of 50 blinded patient samples: pregnant women with thrombocytopenia (Group 1A, n=11), thrombocytopenic women after delivery (Group 1B, n=9) and healthy women with a thrombocytopenic newborn (Group 2, n=30). Group 1A displayed higher median FL1 (mean 306, CI 279–332) as compared to that of Group 2 (mean 266, CI 255–277; p=0.0038) or to that of the female controls (mean 249, CI 231–268; p<0.001). Relative FL1 was also higher in the patients of Group 1A than those of Group 2 (p=0.037). When analysing the % RP, the difference between these groups was not significant. In the patients (n=50), the median FSC (mean 407, SD 40, CI 395–418) was also higher than that of the controls (n=54; mean 383, SD 25, CI 376–390; Mann–Whitney U‐test, p=0.0015). In Group 1A, a significant correlation was observed between the Patient median FL1 and Patient median FSC (r=0.62, p=0.043). When developing methods for the measurement of RP, it seems to be useful to analyse the data with more than one principle to define the threshold limit for TO positivity.

Great discrepancy in antithrombin activity measured using five commercially available functional assays

INTRODUCTION Congenital antithrombin (AT) deficiency is an inherited thrombophilia with high thrombosis prevalence. It has been reported that functional laboratory tests have varying potential in recognizing type II defects, and that there is discrepancy between thrombin inhibition based and factor Xa inhibition based methods. MATERIALS AND METHODS Patients with known AT deficiency (n=374) were interviewed and their current AT status was tested in a new blood sample (n=214). The samples were analyzed using five different commercial methods (either thrombin or FXa based and one thrombin based method using two different incubation times). Antigen assay was used for typing the deficiency. RESULTS In 101 of 214 (47.2%) samples the results obtained by different methods were congruent: 91 low and 10 normal by all assays. All other 113 (52.8%) samples showed discrepant values between the assays: most of them had abnormal results by two methods and normal by other methods. The discrepancies were observed mainly in type II deficiency. The best correlation of results was observed between one thrombin based and one FXa based assay. CONCLUSIONS There was great inter-assay variability especially in type II deficient patients, but also in patients with type I deficiency. However, most of the patients defined as having normal AT activity by some methods had thrombotic symptoms. Most tested assays find type I AT deficient patients accurately. In our study population only methods A1 and C could find most patients with type II AT deficiency, whereas methods A2, B and D misdiagnosed the majority of patients as non-deficient.

Genetic polymorphism H131R of Fcγ receptor type IIA (FcγRIIA) in a healthy Finnish population and in patients with or without platelet-associated IgG

Abstract: Patients (n = 113) with histories of thrombocytopenia and with different profiles for platelet‐associated IgG (PA‐IgG) were subdivided according to the genetic polymorphism H131R in the Fcγ receptor type IIA (FcγRIIA). PA‐IgG was measured by the direct platelet immunofluorescence test (PIFT), and GP IIbIIIa and/or GP Ib‐specific PA‐IgG was investigated by a modified version of the direct monoclonal antibody‐specific immobilization of platelet antigens (MAIPA) assay. As a control, the distribution of FcγRIIA polymorphism H131R was determined among 93 healthy Finnish blood donors. The frequencies for H131 and R131 were 0.56 and 0.44 (CI: 0.37–0.51), respectively, which did not differ significantly from those in other Caucasian populations. The distribution of the genotypes HH131, HR131 and RR131 in the patients and controls did not differ significantly. In the HH131 group, the PA‐IgG was higher than in the RR131 group (p = 0.082). Female patients with the genotype RR131 seemed to be younger than those with HH131 (p = 0.065). Among the female patients, a significantly greater number were under 40 yr old in the RR131 group than in the HH131 group (p = 0.0060). Within the RR131 group, the female patients were far younger than the male patients (median 29 vs. 61 yr; p = 0.0021). The results point to the heterogeneity of immune thrombocytopenia, which may partly explain the poor predictive value of PA‐IgG studies.

Usefulness of maternal anti-HPA-1a antibody quantitation in predicting severity of foetomaternal alloimmune thrombocytopenia

To study the clinical usefulness of maternal anti‐HPA‐1a antibody levels in predicting severe foetomaternal alloimmune thrombocytopenia (FMAIT).