Maternal anti-HLA class I antibodies are associated with reduced birth weight in thrombocytopenic neonates.

In this comparative cross-sectional study, possible associations between maternal anti-HLA class I antibodies and birth weight in neonatal thrombocytopenia are explored. Although commonly detected in pregnancies and generally regarded as harmless, it has been suggested that such antibodies might be associated with fetal and neonatal alloimmune thrombocytopenia (FNAIT). As a link between FNAIT due to human platelet antigen 1a-specific antibodies and reduced birth weight in boys has previously been demonstrated, we wanted to explore whether maternal anti-HLA class I antibodies might also affect birth weight. To examine this, suspected cases of FNAIT referred to the Norwegian National Unit for Platelet Immunology during the period 1998-2009 were identified. Pregnancies where the only finding was maternal anti-HLA class I antibodies were included. An unselected group of pregnant women participating in a prospective study investigating maternal-fetal hemodynamics at the University Hospital North Norway during the years 2006-2010 served as controls. Twenty-nine percent of controls had anti-HLA class I antibodies. The thrombocytopenic neonates had a significantly lower adjusted birth weight (linear regression, P=0.036) and significantly higher odds of being small for gestational age (OR=6.72, P<0.001) compared with controls. Increasing anti-HLA class I antibody levels in the mother were significantly associated with lower birth weight and placental weight among thrombocytopenic neonates, but not among controls. These results indicate that maternal anti-HLA class I antibodies in thrombocytopenic neonates are associated with reduced fetal growth. Further studies are needed to test if placental function is affected.

True risk of fetal/neonatal alloimmune thrombocytopenia in subsequent pregnancies: a prospective observational follow-up study.

OBJECTIVES: To assess neonatal platelet counts by comparing alloimmunised pregnancies from a Norwegian screening and intervention study with subsequent pregnancies from the same women. DESIGN: Prospective observational follow-up study. SETTING: A university hospital. POPULATION: HPA-1a immunised women from a large Norwegian screening study that gave birth to one or more children after the screening study ended (2004-2012). METHODS: Follow-up of maternal anti-HPA-1a antibody levels and neonatal platelet counts from the screening pregnancies were compared with subsequent pregnancies. None of the women received antenatal intravenous immunoglobulin (IVIG) treatment and neonatal platelet counts were therefore comparable. MAIN OUTCOME MEASURES: Change in neonatal platelet counts from one HPA-1a incompatible pregnancy to the next. Maternal anti-HPA-a1 antibody levels from one HPA-1a incompatible pregnancy to the next. RESULTS: Forty-five incompatible subsequent pregnancies were identified. Overall, the neonatal platelet count in the subsequent pregnancy was improved (18%), unchanged (52%), or worse (30%), compared with the corresponding screening pregnancy. There was one case of fetal intracranial haemorrhage (ICH) identified in the screening (intrauterine fetal death detected at 30 weeks of gestation) and no ICH cases recorded for the subsequent pregnancies. In cases where the platelet count was lower in the subsequent pregnancy, the maternal anti-HPA-1a antibody level was higher compared with the screening pregnancy. In comparison, the maternal antibody level was lower in subsequent pregnancies where the platelet count improved. CONCLUSIONS: In contrast to what is often stated, we found that the neonatal platelet count was increased or unchanged in the majority of subsequent pregnancies of HPA-1a-immunised women.

Foetal/neonatal alloimmune thrombocytopenia in Egypt; human platelet antigen genotype frequencies and antibody detection and follow-up in pregnancies.

BACKGROUND AND OBJECTIVES: Foetal and neonatal alloimmune thrombocytopenia (FNAIT) is studied mainly in Caucasian populations. Severe thrombocytopenia (<50×10(9)/L) gives risk of haemorrhage and the most feared complication is intracranial haemorrhage (ICH). In Caucasian populations anti-human platelet antigen (HPA)-1a antibodies are the cause of FNAIT in >80% of the cases. The aims of this project were to study the gene frequencies of HPA-1-5 and 15 alleles in an Egyptian population (Arabic), and to determine the frequency of HPA-1a and -5b immunisations in a cohort of Egyptian pregnant women. MATERIALS AND METHODS: Altogether 6974 pregnant women were included in the study. Genotyping was performed by polymerase chain reaction and antibodies were detected by flow cytometry and enzyme-linked immunosorbent assay. HPA-1-5 and 15 alleles were studied in 367 individuals. RESULTS: The HPA genotypes differed from genotypes published from different Caucasian and Chinese (Han) populations in HPA-1, -2, -3, and -5 systems with significant higher frequency of HPA-1b, -2b and -5b. The rate of HPA-1a alloimmunisation was found comparable to Caucasian populations. Severe thrombocytopenia was found in two newborns. No bleeding complication was reported. Anti-HPA-5b antibodies were detected in 4.4% of the pregnant women. Clinical consequences of these antibodies were not studied. CONCLUSION: The HPA-1bb and -5bb genotypes are more frequent in the Egyptian Arabic population studied compared to Caucasian populations. FNAIT due to anti-HPA-1a and -5b antibodies must be suspected in cases of neonatal thrombocytopenia. Further large prospective studies are needed to increase the knowledge of clinical complications related to HPA alloantibodies in populations with different genetic backgrounds.

Neonatal alloimmune thrombocytopenia is not what it was: a lesson learned from a large prospective screening and intervention program.

Controversies regarding the pathophysiology of neonatal alloimmune thrombocytopenia (NAIT) has hampered the development of consensus about how to identify, follow up and treat the women and children with this serious complication. One reason for this is that knowledge about the condition derived from previous retrospective studies do not necessarily conform with data derived from prospective investigations. The main obstacle to introduction of general screening programs to identify the pregnancies to treat, have been lack of reliable risk factors, and an effective treatment. Now, several recent prospective screening programs including up to 100,000 pregnant women has changed the understanding of the NAIT-pathology, and has shown that we are close to answering these critical questions.

Neonatal alloimmune thrombocytopenia in Norway: poor detection rate with nonscreening versus a general screening programme.

The implementation of an antenatal screening programme for neonatal alloimmune thrombocytopenia (NAIT) is currently under debate. We evaluated the detection rate for NAIT in a nonscreened population of 661,200 births where NAIT was diagnosed on clinical indication. We did a cross-sectional comparison with a population of 100,448 human platelet antigen 1a (HPA1a)-screened pregnancies from three of the five health regions in Norway. In a nonscreening situation, 7.5 cases of NAIT were detected per year compared with 53 cases when screening was applied. The detection rate of NAIT in Norway was therefore 14% of the expected rate.

Monoclonal platelet antigen capture assays (MAIPA) and reagents: a statement.

This statement concerning the monoclonal-specific immobilization of platelet antigens (MAIPA) has been written on behalf of the International Society of Blood Transfusion--Working Party on Platelet Immunology. The MAIPA technique is considered as the gold standard reference technique in platelet immunology. The assay performed with reagents labelled for 'research only' is acceptable as long as it is regularly evaluated by participation of laboratories in national or international workshops held with reference laboratories.

Cost-effectiveness of antenatal screening for neonatal alloimmune thrombocytopenia.

OBJECTIVES: To estimate the costs and health consequences of three different screening strategies for neonatal alloimmune thrombocytopenia (NAIT). DESIGN: Cost-utility analysis on the basis of a decision tree that incorporates the relevant strategies and outcomes. SETTING: Three health regions in Norway encompassing a 2.78 million population. POPULATION: Pregnant women (n = 100,448) screened for human platelet antigen (HPA) 1a and anti-HPA 1a antibodies, and their babies. METHOD: Decision tree analysis. In three branches of the decision tree, pregnant women entered a programme while in one no screening was performed. The three different screening strategies included all HPA 1a negative women, only HPA 1a negative, HLA DRB3*0101 positive women or only HPA 1a negative women with high level of anti-HPA 1a antibodies. Included women underwent ultrasound examination and elective caesarean section 2-4 weeks before term. Severely thrombocytopenic newborn were transfused immediately with compatible platelets. MAIN OUTCOME MEASUREMENTS: Quality-adjusted life years (QALYs) and costs. RESULTS: Compared with no screening, a programme of screening and subsequent treatment would generate between 210 and 230 additional QALYs among 100,000 pregnant women, and at the same time, reduce health care costs by approximately 1.7 million euros. The sensitivity analyses indicate that screening is cost effective or even cost saving within a wide range of probabilities and costs. CONCLUSION: Our calculations indicate that it is possible to establish an antenatal screening programme for NAIT that is cost effective.

Selecting and deselecting imatinib-resistant clones: observations made by longitudinal, quantitative monitoring of mutated BCR-ABL.

Resistance to imatinib during the treatment of chronic myeloid leukaemia (CML) is frequently associated with point mutations in the ABL gene encoding the ATP binding region likely to cause disease relapse. Early diagnosis and monitoring of these mutations may be important in order to prevent rapid expansion of resistant clones. We describe a quantitative mutation-specific PCR assay based on the readily available Taqman platform. Selectivity for the mutated target is conferred by mutation-specific primers destabilised by additional mismatches. The assay can be carried out in parallel to standard BCR-ABL quantification and is therefore more quickly compared to standard sequencing procedures. The sensitivity of the assay reaches 0.1%. It also allows for quantitative assessment of mutated clones. By analysing sequential samples of resistant subjects, we show how mutated clones were selected, maintained or deselected depending on the individual treatment setting. The high sensitivity and practical merits of this method makes it a good candidate for prospective molecular surveillance of patients at high risk for imatinib resistance.

Coeliac disease in subjects with secondary hyperparathyroidism.

OBJECTIVE: Coeliac disease (CD) may present in its classical form with diarrhoea and weight loss, but also with atypical symptoms that are both related and unrelated to malabsorption. Osteomalacia or osteopenia following malabsorption of calcium and vitamin D is known to occur in patients with CD, and in such cases secondary hyperparathyroidism (SHP) caused by low serum calcium levels is frequently found. However, the prevalence of CD in subjects with SHP has not been reported. MATERIAL AND METHODS: In the Tromsø study 2001, serum parathyroid hormone (PTH) and calcium were measured in 7954 subjects of whom 6061 were eligible for follow-up. From this group, 97 subjects with SHP (serum PTH> or =6.5 pmol/l and serum calcium <2.40 mmol/l) and 104 matched control subjects were re-examined with serological tests for CD (anti-tissue transglutaminase, anti-gluten IgA and IgG). RESULTS: CD was diagnosed in 4 subjects, all from the original SHP group. At the re-examination, only 29 of the 97 subjects with SHP still had elevated serum PTH levels. Among these were 3 of the subjects with CD. When grouping the serological test results as negative, borderline or positive, there was a significant difference between the SHP group and the controls for anti-tissue transglutaminase and anti-gluten IgA (p<0.05). CONCLUSIONS: Subjects with SHP, at least when SHP is persistent, should be tested for CD.

[Significance of maternal alloantibodies for neonatal thrombocytopenia]. / Maternelle alloantistoffers betydning ved trombocytopeni hos nyfødte.

BACKGROUND: Thrombocytopenia has been shown to be present in about 1% of unselected newborns. Alloantibodies to platelets induce the most severe thrombocytopenia. MATERIAL AND METHODS: Samples from 195 mothers who had just given birth to thrombocytopenic children, were analysed by platelet antigen genotyping and detection of platelet specific antibodies. RESULTS: 75 mothers were typed human platelet antigen (HPA) 1bb, and in 65 mother, anti-HPA 1a antibodies could be detected. Anti-HPA 5b antibodies were detected in three samples and anti-HLA antibodies in 73 samples. INTERPRETATION: Alloantibodies were shown to be an important cause of thrombocytopenia in the new-born children and anti-HPA 1a antibodies were, as expected, the most common platelet-specific antibody involved. Anti-HLA class 1 antibodies were detected as the only antibody in 51 cases of thrombocytopenia. Though it is not yet formally shown, this may indicate that anti-HLA class 1 antibodies may cause thrombocytopenia in the fetus and new-born. Based on the assumption that neonatal alloimmune thrombocytopenia is present in 1:1,000 new-born, 25% of the neonatal alloimmune thrombocytopenia cases in Norway are verified by laboratory analysis. Alloantibodies to thrombocytes are of clinical importance in future pregnancies and transfusions. The cost and benefit of a national screening program for anti-HPA 1a antibodies in all pregnant women should be carefully considered.

Neonatal alloimmune thrombocytopenia due to anti-HPA 1a antibodies; the level of maternal antibodies predicts the severity of thrombocytopenia in the newborn.

Eleven thousand one hundred pregnant women were genotyped for human platelet antigen HPA 1, and 198 HPA 1bb women were followed in the pregnancy with quantitative assay for anti-HPA la antibodies. Antibodies were detected in 24 women, and nine children were born with severe thrombocytopenia (< 50x10(9)/L). All mothers with high levels of antibodies were delivered of children with severe thrombocytopenia. None of the newborn infants had clinical signs of intra-cranial haemorrhage. The level of maternal anti-HPA 1a antibodies is predictive for fetal thrombocytopenia and may be used in decisions related to time and mode of delivery.

[Decentralized high-dose cytostatic treatment with autologous stem cell support]. / Regionalisert høydose cellegiftbehandling med autolog stamcellestøtte.

In the past high-dose chemotherapy with autologous stem cell support in the treatment of certain types of cancer, was centralized to two hospitals in Norway. Almost three years ago it was decided that the treatment should be offered by all five university hospitals. In the northernmost university hospital of Norway, Tromsø, peripheral stem cells were harvested from 29 patients after successful mobilization with chemotherapy and granulocyte colony-stimulating factor (G-CSF). After high-dose chemotherapy, more than 2 x 10(6) CD34-positive stem cells/kg were transplanted in 24 patients and a sign of reconstitution of bone marrow function was achieved with mean time for neutrophils > 0.5x10(9)/l, 9.8 days and for platelets > 20x10(9)/l, 10.8 days. No treatment-related deaths have occurred. Transplantation of selected CD34-positive stem cells has been performed in one patient. Recovery was comparable to the recovery of patients who had undergone transplantation with unselected products. This indicates that even small centres performing as few as ten procedures per year may offer high-dose chemotherapy with autologous stem cell support safely and successfully.

One-tube method for complete HPA-1 genotyping by PCR using sequence-specific primers.

Human platelet antigens (HPA) can be targets for antibody responses that cause life-threatening thrombocytopenia following platelet transfusions or pregnancy. As an aid to diagnosis and prevention, serologic and DNA-based methods have been developed to type HPA. Of the DNA-based strategies, those using the polymerase chain reaction (PCR) are very sensitive, but often require processing of amplification products. Sequence-specific primers (SSP) in the PCR eliminate the need for extensive handling of reaction products beyond gel electrophoresis. However, current methods require a separate reaction for each allele being typed. In this report we describe a method to simultaneously and completely genotype both alleles of HPA-1 in a single PCR. In addition, because the absence of an amplification product might also show the failure of a SSP, we introduced a recombinant template that can only be amplified by the SSP, thus ensuring primer performance and the identified genotype.

A dinucleotide deletion in exon 4 of the PlA2 allelic form of glycoprotein IIIa: implications for the correlation of serologic versus genotypic analysis of human platelet alloantigens.

Platelets from a patient with a suspected case of posttransfusion purpura were subjected to alloantigen phenotyping and found to express the PlA1, but not the PlA2, allelic form of human platelet membrane glycoprotein (GP) IIIa on the platelet surface. However, genotyping showed unambiguously that the patient carried the genes for both of these GPIIa alleles. Based on these results, we postulated that the PlA2 allele was silent, ie, that this patient was a carrier for Glanzmann thrombasthenia (GT). Quantitative analysis of GPIIb-IIIa surface expression showed only 20,000 GPIIb-IIIa receptors/platelet, approximately half of the value obtained with control platelets. Southern blot analysis showed no large deletions or insertions within the GPIIIa gene, and amplification of all 14 exons encoding GPIIIa resulted in the production of normal sized polymerase chain reaction (PCR) products in all cases. DNA-sequence analysis showed an AG dinucleotide deletion affecting codons 210 and 211 within exon 4 of the GPIIIa gene, leading to a change in reading frame and the creation of a stop codon 38 nucleotides down-stream. The predicted truncated protein consists of only the first 223 of the normal 762 amino acids, thus accounting for the failure to express the PlA2 allele on the platelet surface. While encountered only rarely, carriers of either GT or Bernard Soulier syndrome that are at the same time heterozygous for human platelet alloantigenic epitopes found on GPIb, GPIIb, or GPIIIa have the possibility to give discrepant results when comparing genotypic versus phenotypic analysis. In such situations, the combination of serologic and DNA-based evaluation contributes complementary and beneficial diagnostic information than either one alone are able to provide.

[Neonatal alloimmune thrombocytopenia. Diagnosis and follow-up in pregnancy]. / Neonatal alloimmun trombocytopeni. Diagnostikk, og oppfølging i svangerskapet.

Neonatal alloimmune thrombocytopenia is present in every 2,000-3,000 pregnancy, that is in 20-30 pregnancies in Norway each year. Anti-HPA la antibodies are usually present in severe alloimmune thrombocytopenia in foetus and neonates. Pregnant women are not screened for the presence of anti-HPA la antibodies. Neonatal alloimmune thrombocytopenia can be suspected in newborn children who show signs or symptoms of thrombocytopenia. Laboratory investigation for neonatal alloimmune thrombocytopenia should be performed if the newborn child shows signs of bleeding, in women who have had multiple abortions and after stillbirth. Examples are presented from laboratory investigations in seven families with children who have thrombocytopenia.

Flow cytometric analysis in platelet crossmatching using a platelet suspension immunofluorescence test.

BACKGROUND: The sensitivity of flow cytometric measurement of platelet antibodies in a crossmatch technique was investigated. STUDY DESIGN AND METHODS: The corrected count increment after platelet transfusion was compared with the fluorescence ratio determined by flow cytometric measurement. RESULTS: When crossmatching was performed before transfusion(s) in alloimmunized patients, a fluorescence ratio < or = 1.7 was associated with satisfactory responses (corrected count increment > or = 7.5), and the predictive values for negative and positive crossmatch results were 94 and 87 percent, respectively. Analysis of antigen preservation during platelet storage with antibodies to HLA alpha-chain, HLA-B27, HPA-1a, and HPA-3a showed that platelets can be stored, refrigerated, for up to 4 weeks without significant loss of HLA class I and HPA-1a. There was a slight but continuous loss of HPA-3a upon storage. CONCLUSION: Flow cytometric measurement of fluorescence in the platelet suspension immunofluorescence test can be used for platelet crossmatching, with sensitivity and predictive values comparable to those of previously described techniques and with the advantage of automation.

Rapid determination of platelet alloantigen genotypes by polymerase chain reaction using allele-specific primers.

BACKGROUND: The technique of allele-specific polymerase chain reaction (PCR) amplification has been adapted for DNA-based human platelet alloantigen typing. STUDY DESIGN AND METHODS: Sequence-specific primers were used to discriminate between the alleles encoding the six major human platelet alloantigens in a series of patients and normal blood donors. RESULTS: This technique allows the direct determination of platelet antigen genotypes from genomic DNA after PCR amplification and agarose gel electrophoresis. It offers significant advantages over previously described techniques for alloantigen identification, as the additional analytical steps of restriction enzyme digestion or dot blot hybridization are not required. The results obtained with this technique correlated precisely with those derived from serologic typing and allele-specific oligonucleotide hybridization. CONCLUSION: The use of allele-specific PCR for platelet alloantigen typing should facilitate the development of DNA-based typing in other regional blood centers and clinical laboratories.

High-density lipoprotein has different binding capacity for different apoproteins. The amyloidogenic apoproteins are easier to displace from high-density lipoprotein.

Purified human amyloid protein A (AA) or serum amyloid protein A (SAA) was incubated with normal human high-density lipoprotein (HDL). After ultracentrifugation the amount of AA or SAA associated with HDL was measured. It was found that the binding capacity of HDL for SAA was higher than that for AA. Incubation of these in vitro associated HDL-AA and HDL-SAA complexes with purified apo AI or apo AII resulted in varying degrees of displacement of the associated AA or SAA from HDL. Under the experimental conditions used, apo AI was able to displace AA from HDL, while apo AII was able to displace both SAA and AA. This indicates that the binding capacity of HDL is different for SAA and AA. Mouse acute-phase HDL was isolated and the native complexes were incubated with human apo AII. SAA2, the amyloidogenic SAA variant in mice, was displaced from HDL to a greater extent than SAA1, indicating a lower binding capacity for the amyloidogenic SAA variant for the HDL complexes.