Systematic review of the measurement properties of indices of prenatal care utilization

Background

An accurate assessment of the adequacy of prenatal care utilization is critical to inform the relationship between prenatal care and pregnancy outcomes. This systematic review critically appraises the evidence on measurement properties of prenatal care utilization indices and provides recommendations about which index is the most useful for this purpose.

Methods

MEDLINE, EMBASE, CINAHL, and Web of Science were systematically searched from database inception to October 2018 using keywords related to indices of prenatal care utilization. No language restrictions were imposed. Studies were included if they evaluated the reliability, validity, or responsiveness of at least one index of adequacy of prenatal care utilization. We used the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist. We conducted an evidence synthesis using predefined criteria to appraise the measurement properties of the indices.

Results

From 2664 studies initially screened, 13 unique studies evaluated the measurement properties of at least one index of prenatal care utilization. Most of the indices of adequacy of prenatal care currently used in research and clinical practice have been evaluated for at least some form of reliability and/or validity. Evidence about the responsiveness to change of these indices is absent from these evaluations. The Adequacy Perinatal Care Utilization Index (APNCUI) and the Kessner Index are supported by moderate evidence regarding their reliability, predictive and concurrent validity.

Conclusion

The scientific literature has not comprehensively reported the measurement properties of commonly used indices of prenatal care utilization, and there is insufficient research to inform the choice of the best index. Lack of strong evidence about which index is the best to measure prenatal care utilization has important implications for tracking health care utilization and for formulating prenatal care recommendations.

Genetic diagnosis in recently transfused patients

Analysis of recently transfused patients is usually postponed to avoid spurious results because of contamination with donor's cells. However, little is known about the extent of this influence in routine molecular diagnostic tests. To elucidate this question, we tested a mix of blood samples from 2 α-1-antitrypsin-deficient patients diagnosed as Pi*Z homozygous with 1 normal donor at 1:1, 1:10, 1:20, and 1:30 proportions. Human identification panel and Pi*Z allele detection were used to establish the detection limit of a blood mixture. Mixtures of 1:1 and 1:10 were easily detected with both techniques, whereas for 1:30, it was necessary to change the equipment settings to identify the mixture. Moreover, the heterozygous pattern observed for the mixtures on Pi*Z genotyping was weaker at this level of mixture. We further evaluated the degree of mixture detectable in 20 transfused patients who received 1 blood unit (concentrate of irradiated or nonirradiated red blood cells) using the human identification panel. Two days after the transfusion, the presence of the donor's markers was not detected, suggesting that after this time point the levels of admixture are below 1:30. The methods applied in the present study showed adequate sensitivity to identify alleles of the so-called "smaller population" of cells up to 3%, approximately. The same result was obtained in a "diagnostic situation," in which the blood mixture was submitted to a PCR-RFLP protocol to detect a mutation.

Alpha 1 antitrypsin deficiency in children with chronic liver disease in North India

OBJECTIVE

We attempted to determine the role of alpha-1-antitrypsin (AAT) deficient variants as an etiologic factor for chronic liver disease in North Indian children.

DESIGN

This study investigated 1700 children (682 retrospectively and 1018 prospectively) (840 CLD, 410 neonatal cholestasis and 450 without liver disease) for AAT deficiency.

SETTING

Tertiary referral center, All India Institute of Medical Sciences, New Delhi.

PATIENTS

Of 1250 liver disease patients, 98 (7.8%) were suspected to be AAT deficient on the basis of screening tests (low serum AAT levels and/or absent/faint alpha-1-globulin band on serum agarose electrophoresis and/or diastase resistant PAS positive granules on liver biopsy).

MAIN OUTCOME MEASURES

AAT deficient Z or S allele in suspected patients.

RESULTS

Z or S allele was not observed on phenotyping (1700 subjects), or with PCR-RFLP, SSCP and sequencing done in 50 of 98 suspected AAT deficient patients. A novel mutation G-to-A at position 333 in exon V was found in two siblings having positive immunohistochemistry for AAT on liver biopsy, both of whom had significant liver disease with portal hypertension.

CONCLUSION

In conclusion, AAT deficiency as an etiologic factor for chronic liver disease in childhood appeared to be uncommon in North India.

Development and characterization of reference materials for MTHFR, SERPINA1, RET, BRCA1, and BRCA2 genetic testing

Well-characterized reference materials (RMs) are integral in maintaining clinical laboratory quality assurance for genetic testing. These RMs can be used for quality control, monitoring of test performance, test validation, and proficiency testing of DNA-based genetic tests. To address the need for such materials, the Centers for Disease Control and Prevention established the Genetic Testing Reference Material Coordination Program (GeT-RM), which works with the genetics community to improve public availability of characterized RMs for genetic testing. To date, the GeT-RM program has coordinated the characterization of publicly available genomic DNA RMs for a number of disorders, including cystic fibrosis, Huntington disease, fragile X, and several genetic conditions with relatively high prevalence in the Ashkenazi Jewish population. Genotypic information about a number of other cell lines has been collected and is also available. The present study includes the development and commutability/genotype characterization of 10 DNA samples for clinically relevant mutations or sequence variants in the following genes: MTHFR; SERPINA1; RET; BRCA1; and BRCA2. DNA samples were analyzed by 19 clinical genetic laboratories using a variety of assays and technology platforms. Concordance was 100% for all samples, with no differences observed between laboratories using different methods. All DNA samples are available from Coriell Cell Repositories and characterization information can be found on the GeT-RM website.

Avaliação da concentração de alfa 1-antitripsina e da presença dos alelos S e Z em uma população de indivíduos sintomáticos respiratórios crônicos

OBJETIVO: Determinar a concentração de alfa 1-antitripsina (AAT) e a prevalência dos alelos S e Z em indivíduos sintomáticos respiratórios crônicos. MÉTODOS: Pacientes com tosse crônica e dispnéia foram submetidos à avaliação clínica, espirometria, tomografia computadorizada de tórax, dosagem de AAT por nefelometria e pesquisa das mutações S e Z por reação em cadeia da polimerase. Foram consideradas como variáveis dependentes a concentração de AAT e o tabagismo. RESULTADOS: Dos 89 pacientes incluídos no estudo (44 mulheres; idade média, 51,3 ± 18,2 anos), os alelos S e Z foram detectados em 33,3% e 5,7%, respectivamente, com freqüência gênica dos alelos S e Z de 0,16 e 0,028. Dois pacientes tinham genótipo SZ (AAT < 89 mg/dL). Os pacientes foram divididos em grupos segundo a concentração de AAT: < 89 mg/dL (deficiência, nenhum grupo); 90-140 mg/dL (faixa intermediária, Grupo 1, n = 30); e > 141 mg/dL (normal, Grupo 2, n = 57). A freqüência de fumantes foi igual nos dois grupos, com carga tabágica maior no Grupo 2. O alelo S estava presente em 13 e 14 pacientes dos Grupos 1 e 2, respectivamente, enquanto que o alelo Z estava presente em 2 e 1 paciente dos mesmos grupos. Não houve diferença nos testes de função pulmonar, nem na freqüência de bronquiectasias ou enfisema entre os dois grupos. Os valores espirométricos e as concentrações de AAT foram similares entre fumantes e não-fumantes. Bronquiectasias foram mais freqüentes entre os não fumantes, e enfisema foi mais freqüente entre os fumantes. CONCLUSÕES: Trinta pacientes apresentaram níveis de AAT abaixo da média esperada para os genótipos MM e MS, e este fato não pode ser explicado por uma freqüência maior dos alelos S e Z.

Molecular analysis of the Pi*Z allele in patients with liver disease

Alpha1-antitrypsin (AAT) is the main protease inhibitor in human plasma. There are more than 75 variants of this protein that differ from each other by their isoelectric point. Most of these alleles cause a reduction in AAT levels; the most common allele is Pi*Z. The main complications related to the Pi*Z allele are obstructive pulmonary disease and liver disease. Some Pi*Z allele carriers present cholestatic jaundice and cirrhosis. The Z type is associated with a secretion defect, which leads to deficiency of AAT and to the formation of intrahepatocytic inclusions in affected subjects. The diagnosis of AAT deficiency can be made by different techniques, including molecular analysis, although the final diagnosis should be done in conjunction with demonstration of the periodic acid-Schiff-positive globules on liver biopsy. In this study, specimens of 29 patients with cryptogenic cirrhosis between age 1 month and 18 years, and of 100 controls were submitted to polymerase chain reaction followed by digestion with TaqI enzyme. Five of the 29 patients had undergone liver transplantation. Three patients were heterozygous for the Pi*Z allele, and two were homozygous (allele frequency = 12.07%; 7/58). Among the controls, who represented the population of Porto Alegre, 1 in 100 individuals was heterozygous for the Pi*Z allele, resulting in an allele frequency of 0.5% (1/200). The high frequency of Pi*Z alleles among the patients indicates the usefulness of AAT molecular testing in children with cholestatic jaundice and cirrhosis.

Epstein-Barr virus (EBV) in Chinese pediatric Hodgkin disease: Hodgkin disease in young children is an EBV-related lymphoma

BACKGROUND

The Epstein-Barr virus (EBV) is thought to be involved in the pathogenesis of some Hodgkin disease (HD) cases. EBV may be associated particularly with childhood HD, a disease rare in the West compared with developing countries. In this study, a large series of Chinese pediatric HD cases has been examined to determine the age-specific prevalence of EBV.

METHODS

Paraffin sections from 104 pediatric and 52 adult Chinese HD cases were examined for EBV-RNA (EBERs) and EBV latent membrane protein-1.

RESULTS

Most pediatric cases arose in boys and showed an histology of mixed cellularity. Prominent interfollicular involvement was seen frequently in the childhood cases. EBV was identified in tumor cells in 113 of 156 (72%) HD cases but was more frequent in pediatric cases (93 of 104; 89%) compared with adult cases (20 of 52; 38%) (P < 0.01; chi-square test). EBV was found in 86 out of 91 (95%) cases in children aged 3-10 years and in 7 out of 13 (54%) cases in children aged 11-14 years (P < 0.01; chi-square test). The virus was less frequent in cases in young adults than in old adults, although this trend was not significant (P > 0.05; chi-square test). Pediatric HD was associated with EBV irrespective of histologic subtype. In adults, EBV was associated more frequently with mixed cellularity than with other subtypes.

CONCLUSION

To the authors' knowledge, this is to date the largest series of pediatric HD cases studied for EBV. Study findings provided further evidence that HD is etiologically heterogeneous. The authors believe that pediatric HD now should be regarded as a distinctive EBV-related lymphoma.

Diagnosis of alpha-1-antitrypsin deficiency by DNA analysis of children with liver disease

BACKGROUND

Alpha-1-antitrypsin deficiency is a genetic disorder which is transmitted in a co-dominant, autosomal form. Alpha-1-antitrypsin deficiency affects mainly the lungs and the liver leading, in the latter case, to neonatal cholestasis, chronic hepatitis or cirrhosis. A precise diagnosis of Alpha-1-antitrypsin deficiency may be obtained by biochemical or molecular analysis.

OBJECTIVE

The purpose of this study was to use DNA analysis to examine the presence of an alpha-1-antitrypsin deficiency in 12 children suspected of having this deficiency and who showed laboratory and clinical characteristics of the disease.

PATIENTS AND METHODS

Twelve patients, aged 3 months to 19 years, who had serum alpha-1-antitrypsin levels lower than normal and/or had hepatic disease of undefined etiology were studied. The mutant alleles S and Z of the alpha-1-antitrypsin gene were investigated in the 12 children. Alpha-1-antitrypsin gene organization was analyzed by amplification of genome through the polymerase chain reaction and digestion with the restriction enzymes Xmnl (S allele) and Taq-1 (Z allele).

RESULTS

Seven of the 12 patients had chronic liver disease of undefined etiology and the other five patients had low serum levels of alpha-1-antitrypsin as well as a diagnosis of neonatal cholestasis and/or chronic liver disease of undefined etiology. Five of the 12 patients were homozygous for the Z allele (ZZ) and two had the S allele with another allele (*S) different from Z.

CONCLUSION

These results show that alpha-1-antitrypsin deficiency is relatively frequent in children with chronic hepatic disease of undefined etiology and/or low alpha-1-antitrypsin levels (41.6%). A correct diagnosis is important for effective clinical follow-up and for genetic counseling.

DNA microarray technology for neonatal screening

Modern molecular biology, owing much to the Human Genome Initiative, has elucidated many of the genetic mechanisms underlying heritable metabolic disease. While the use of molecular methods has flourished in research laboratories, complexity and cost have limited their utility in newborn screening. Newborn blood cards provide high quality DNA samples able to provide reliable support to highly multiplexed polymerase chain reactions (PCR). New manufacturing processes have reduced the cost of DNA microarray technology to the point where it is a practical tool for population screening. In a single assay, a DNA microarray facilitates the co-detection of amplification products diagnostic for several genetic diseases. High throughput is achieved with automation at every step, from DNA extraction to detection of hybrids. We suggest that it is both feasible and practical to develop a first-tier newborn screening protocol based upon multiplex PCR and analysis of amplification products using DNA microarrays. Initial data utilizing the model systems of sickle cell disease, alpha-1-antitrypsin deficiency and Factor V Leiden will be reported.

Clear correlation of genotype with disease phenotype in very-long-chain acyl-CoA dehydrogenase deficiency

Very-long-chain acyl-CoA dehydrogenase (VLCAD) catalyzes the initial rate-limiting step in mitochondrial fatty acid beta-oxidation. VLCAD deficiency is clinically heterogenous, with three major phenotypes: a severe childhood form, with early onset, high mortality, and high incidence of cardiomyopathy; a milder childhood form, with later onset, usually with hypoketotic hypoglycemia as the main presenting feature, low mortality, and rare cardiomyopathy; and an adult form, with isolated skeletal muscle involvement, rhabdomyolysis, and myoglobinuria, usually triggered by exercise or fasting. To examine whether these different phenotypes are due to differences in the VLCAD genotype, we investigated 58 different mutations in 55 unrelated patients representing all known clinical phenotypes and correlated the mutation type with the clinical phenotype. Our results show a clear relationship between the nature of the mutation and the severity of disease. Patients with the severe childhood phenotype have mutations that result in no residual enzyme activity, whereas patients with the milder childhood and adult phenotypes have mutations that may result in residual enzyme activity. This clear genotype-phenotype relationship is in sharp contrast to what has been observed in medium-chain acyl-CoA dehydrogenase deficiency, in which no correlation between genotype and phenotype can be established.

Molecular basis, clinical consequences and diagnosis of alpha-1 antitrypsin deficiency

(1) Deficiency of alpha AT is one of the most common hereditary diseases affecting Caucasians in Europe. The alpha 1AT protein is extremely pleomorphic, and around 90 variants due to mutations have been recognized. The prime functions of alpha 1AT is to inhibit neutrophil elastase, and a proportion of individuals who are deficient in alpha 1AT develop emphysema. The most common deficiency variant (Z) is also associated with liver disease. The main site of alpha 1AT synthesis is in the liver. Not all deficient individuals are affected by lung or liver disease, however, so that other factors (genetic and environmental) are clearly important. (2) Investigation of alpha 1AT status is essential in any child or adult presenting with chronic liver disease. The genetic cause cannot be identified clinically or by any other laboratory investigation. The diagnosis carries important prognostic consequences and is important for other family members. Patients with emphysema should have their Pi type determined, especially if they are under the age of 50, have never smoked or there is a suggestive family history. Asymptomatic individuals who are homozygous type Z should be referred to a chest physician for a clinical and radiological assessment together with lung function tests. (3) Several laboratory tests are available to detect alpha 1AT deficiency, and the choice of test(s) will depend on circumstances. Quantitation of the serum protein is simple and cheap. Because alpha 1AT is an acute phase protein, however, quantitation used in isolation may give false negative results which are clearly unacceptable, particularly in association with paediatric liver disease. Phenotyping by isoelectric focusing requires some experience in distinguishing SZ and ZZ phenotypes, and phenotyping should ideally be used in conjunction with quantitation because heterozygous null phenotypes may appear identical to homozygous normal phenotypes. (4) Prenatal diagnosis is usually performed by DNA analysis of CVS samples obtained at 11-13 weeks. Because of the risk that CVS samples might be contaminated by maternal tissue, assays which are less likely to detect minor contaminants are preferable. At present, use of DNA tests is confined to prenatal diagnosis, but the availability of simple tests and the possibility of unequivocal identification of S and Z alleles means that these tests are likely to find greater use in the near future.

The molecular basis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in compound heterozygous patients: is there correlation between genotype and phenotype?

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most commonly recognized defect of mitochondrial beta-oxidation. It is potentially fatal, but shows a wide clinical spectrum. The aim of the present study was to investigate whether any correlation exists between MCAD genotype and disease phenotype. We determined the prevalence of the 14 known and seven previously unknown non-G985 mutations in 52 families with MCAD deficiency not caused by homozygosity for the prevalent G985 mutation. This showed that none of the non-G985 mutations are prevalent, and led to the identification of both disease-causing mutations in 14 families in whom both mutations had not previously been reported. We then evaluated the severity of the mutations identified in these 14 families. Using expression of mutant MCAD in Escherichia coli with or without co-overexpression of the molecular chaperonins GroESL we showed that five of the missense mutations affect the folding and/or stability of the protein, and that the residual enzyme activity of some of them could be modulated to a different extent depending on the amounts of available chaperonins. Thus, some of the missense mutations may result in relatively high levels of residual enzyme activity, whereas the mutations leading to premature stop codons will result in no residual enzyme activity. By correlating the observed types of mutations identified to the clinical/biochemical data in the 14 patients in whom we identified both disease-causing mutations, we show that a genotype/phenotype correlation in MCAD deficiency is not straightforward. Different mutations may contribute with different susceptibilities for disease precipitation, when the patient is subjected to metabolic stress, but other genetic and environmental factors may play an equally important role.

Rapid and simple diagnosis of the two common alpha 1-proteinase inhibitor deficiency alleles Pi*Z and Pi*S by DNA analysis

We describe a simple DNA-based method to assign the two common alpha 1-proteinase inhibitor (alpha 1-antitrypsin) deficiency alleles in the Pi-system (Pi*Z and Pi*S). Two sets of mutated primers are used in the polymerase chain reaction (PCR), followed by a restriction enzyme digest of the products. The mutated forward primers create a Taq I site only if the wildtype alleles (mostly M or subtypes) are present and not in the presence of the Pi*Z or Pi*S alleles. The reverse primers are mutated for an invariant Taq I site which serves as an internal control site in order to assure the completion of the restriction enzyme digest. The digested PCR products can be clearly resolved by 2.5% MetaPhore-agarose gel electrophoresis. This simple PCR probing of the most common alpha 1-antiproteinase deficiency alleles can be routinely applied either to samples showing quantitatively decreased alpha 1-antiproteinase values in serum or to blood spots of Guthrie cards used for mass screening purposes. In addition, this method may provide the opportunity for a simple, rapid, and reliable prenatal diagnosis of alpha 1-antiproteinase deficiency in special cases.

Ethylmalonic aciduria is associated with an amino acid variant of short chain acyl-coenzyme A dehydrogenase

Ethylmalonic aciduria is a common biochemical finding in patients with inborn errors of short chain fatty acid beta-oxidation. The urinary excretion of ethylmalonic acid (EMA) may stem from decreased oxidation by short chain acyl-CoA dehydrogenase (SCAD) of butyryl-CoA, which is alternatively metabolized by propionyl-CoA carboxylase to EMA. We have recently detected a guanine to adenine polymorphism in the SCAD gene at position 625 in the SCAD cDNA, which changes glycine 209 to serine (G209S). The variant allele (A625) is present in homozygous and in heterozygous form in 7 and 34.8% of the general population, respectively. One hundred and thirty-five patients from Germany, Denmark, the Czech Republic, Spain, and the United States were selected for this study on the basis of abnormal EMA excretion ranging from 18 to 1185 mmol/mol of creatinine (controls < 18 mmol/mol of creatinine). Among them, we found a significant overrepresentation of the variant allele. Eighty-one patients (60%) were homozygous for the A625 allele, 40 (30%) were heterozygous, and only 14 (10%) harbored the wild-type allele (G625) in homozygous form. By overexpressing the wild-type and variant protein (G209S) in Escherichia coli and COS cells, we showed that the folding of the variant protein was slightly compromised in comparison to the wild-type and that the temperature stability of the tetrameric variant enzyme was lower than that of the wild type. Taken together, the over-representation and the biochemical studies indicate that the A625 allele confers susceptibility to the development of ethylmalonic aciduria.

Polymerase chain reaction-mediated site-directed mutagenesis detection of Z and S alpha-1-antitrypsin alleles in family members

Alpha-1-antitrypsin (A1AT) deficiency is an autosomal hereditary disorder with a reduction in serum A1AT levels. In a large family, we used a polymerase chain reaction (PCR)-mediated, site-directed mutagenesis assay to detect the two most common A1AT deficient variants, Z and S. By coamplification, using primers for both the Z and S mutations, we were able to detect heterozygous and homozygous genotypes for both mutations in a single reaction. We compared our results with phenotype studies obtained by standard immunofixation and isoelectric focusing techniques at two reference laboratories. Whereas PCR and isoelectric focusing agreed completely, there were five discrepancies in the results obtained by the immunofixation procedure. The reference laboratory that provided these discrepant results later informed us of a quality control problem that accounted for their error. The family study included 12 individuals representing three generations. Two individuals were MM homozygotes, three were MZ heterozygotes, four were MS heterozygotes, and three were SZ heterozygotes. A thirteenth family member was diagnosed as a ZZ homozygote at another institution. We have shown that this PCR coamplification technique provides accurate information about the M, S, and Z alleles that is at least as useful as current reference laboratory methodologies.