Modification to reporting of qualitative fluorescent spot test results improves detection of glucose-6-phosphate dehydrogenase (G6PD)-deficient heterozygote female newborns

Differential Diagnosis of Rare Diseases Involving Bilateral Lower Extremities with Similar 99mTc-MDP Bone Scan Patterns: Analysis of a Case Series

Here, we reported a panel of rare diseases involving bilateral lower extremities with similar imaging patterns on 99mTc-MDP bone scans. Glucose-6-phosphate dehydrogenase deficiency (G-6PD deficiency), Gaucher disease (GD), steroid-induced osteonecrosis, progressive diaphyseal dysplasia (PDD), Erdheim–Chester disease (ECD) and Langerhans cell sarcoma (LCS) were included and imaging characteristics were analyzed. The rare properties of these diseases and mimicking features on 99mTc-MDP bone scans rendered differential diagnosis difficult but necessary. We believe that the rarely known imaging features of the reported diseases will undoubtedly help nuclear medicine physicians make differential diagnoses in clinical practice.

Evaluation of quantitative biosensor for glucose-6-phosphate dehydrogenase activity detection

Neonatal jaundice is a common and severe disease in premature infants with Glucose-6-Phosphate Dehydrogenase (G-6-PD) deficiency. The World Health Organization (WHO) has recommended screening for G-6-PD deficiency in newborns for early recognition as well as to prevent unwanted outcomes in a timely manner. The present study aimed to assess a point-of-care, careSTARTTM G6PD biosensor as a quantitative method for the diagnosis of G-6-PD deficiency. Factors influencing the evaluation of G-6-PD enzyme activity were examined in 40 adults, including ethylenediaminetetraacetic acid (EDTA) anticoagulant, hematocrit concentration, storage temperature and time. Analytic performance of the careSTARTTM G6PD biosensor was evaluated in 216 newborns and compared with fluorescent spot test (FST) and standard quantitative G-6-PD enzyme activity (SGT) assay. The results of factors affecting the G-6-PD enzyme activity showed that the activity determined from finger-prick was not statistically different from venous blood (p = 0.152). The G-6-PD value was highly dependent on the hematocrit and rose with increasing hematocrit concentration. Its activity was stable at 4°C for 3 days. Reliability analysis between the careSTARTTM G6PD biosensor and SGT assay showed a strong correlation with a Pearson's correlation coefficient of 0.82 and perfect agreement by intraclass correlation coefficient (ICC) of 0.90. Analysis of the area under the Receiver Operating Curve (AUC) illustrated that the careSTARTTM G6PD biosensor had 100% sensitivity, 96% specificity, 73% positive predictive value (PPV), 100% negative predictive value (NPV) and 97% accuracy at 30% of residual activity. While the diagnostic ability for identifying G-6-PD deficiency had 78% sensitivity, 89% specificity, 56% positive predictive value (PPV), 96% negative predictive value (NPV) and 88% accuracy when stratified by gender. The careSTARTTM G6PD biosensor is an attractive option as a point-of-care quantitative method for G-6-PD activity detection. Quantification of G-6-PD enzyme activity in newborns is the most effective approach for the management of G-6-PD deficiency to prevent severe jaundice and acute hemolysis.

Comparison of Spectrophotometry, Chromate Inhibition, and Cytofluorometry Versus Gene Sequencing for Detection of Heterozygously Glucose-6-Phosphate Dehydrogenase-Deficient Females

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme deficiency worldwide. Detection of heterozygously deficient females can be difficult as residual activity in G6PD-sufficient red blood cells (RBCs) can mask deficiency. In this study, we compared accuracy of 4 methods for detection of G6PD deficiency in females. Blood samples from females more than 3 months of age were used for spectrophotometric measurement of G6PD activity and for determination of the percentage G6PD-negative RBCs by cytofluorometry. An additional sample from females suspected to have G6PD deficiency based on the spectrophotometric G6PD activity was used for measuring chromate inhibition and sequencing of the G6PD gene. Of 165 included females, 114 were suspected to have heterozygous deficiency. From 75 females, an extra sample was obtained. In this group, mutation analysis detected 27 heterozygously deficient females. The sensitivity of spectrophotometry, cytofluorometry, and chromate inhibition was calculated to be 0.52 (confidence interval [CI]: 0.32-0.71), 0.85 (CI: 0.66-0.96), and 0.96 (CI: 0.71-1.00, respectively, and the specificity was 1.00 (CI: 0.93-1.00), 0.88 (CI: 0.75-0.95), and 0.98 (CI: 0.89-1.00), respectively. Heterozygously G6PD-deficient females with a larger percentage of G6PD-sufficient RBCs are missed by routine methods measuring total G6PD activity. However, the majority of these females can be detected with both chromate inhibition and cytofluorometry.

Diagnostic approaches for inherited hemolytic anemia in the genetic era

Inherited hemolytic anemias (IHAs) are genetic diseases that present with anemia due to the increased destruction of circulating abnormal RBCs. The RBC abnormalities are classified into the three major disorders of membranopathies, hemoglobinopathies, and enzymopathies. Traditional diagnosis of IHA has been performed via a step-wise process combining clinical and laboratory findings. Nowadays, the etiology of IHA accounts for germline mutations of the responsible genes coding for the structural components of RBCs. Recent advances in molecular technologies, including next-generation sequencing, inspire us to apply these technologies as a first-line approach for the identification of potential mutations and to determine the novel causative genes in patients with IHAs. We herein review the concept and strategy for the genetic diagnosis of IHAs and provide an overview of the preparations for clinical applications of the new molecular technologies.

Dielectrophoresis for Biomedical Sciences Applications: A Review

Dielectrophoresis (DEP) is a label-free, accurate, fast, low-cost diagnostic technique that uses the principles of polarization and the motion of bioparticles in applied electric fields. This technique has been proven to be beneficial in various fields, including environmental research, polymer research, biosensors, microfluidics, medicine and diagnostics. Biomedical science research is one of the major research areas that could potentially benefit from DEP technology for diverse applications. Nevertheless, many medical science research investigations have yet to benefit from the possibilities offered by DEP. This paper critically reviews the fundamentals, recent progress, current challenges, future directions and potential applications of research investigations in the medical sciences utilizing DEP technique. This review will also act as a guide and reference for medical researchers and scientists to explore and utilize the DEP technique in their research fields.

Prevalence of G6PD deficiency and Plasmodium falciparum parasites in asymptomatic school children living in southern Ghana

Background

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked genetic disorder that results in impaired enzyme activity. Although G6PD deficiency is globally distributed it is more prevalent in malaria-endemic countries. Several mutations have been identified in the G6PD gene, which alter enzyme activity. The G6PD genotype predominantly found in sub-Saharan Africa is the G6PDB (G6PD_376A) with (G6PD_376G) and G6PDA- (G6PD_376G/202A, G6PD_376G/542T, G6PD_376G/680T and G6PD_376G/968C) occurring at lower frequencies.

Aim

The aim of this study was to identify the prevalence of G6PD deficiency and asymptomatic Plasmodium falciparum carriage in children living in southern Ghana and determine whether G6PD deficiency influences asymptomatic carriage of P. falciparum parasites.

Methods

Blood samples were obtained once a month from 170 healthy Ghanaian school children aged between 5 and 12 years from Basic schools in two communities Obom and Abura with similar rainfall patterns and malaria peak seasons. G6PD enzyme activity was assessed using the qualitative G6PD RDT kit (AccessBIO). G6PD genotyping and asymptomatic parasite carriage was determined by PCR followed by restriction fragment length polymorphism (RFLP) of DNA extracted from dried blood spots.

Results

The only sub-Saharan G6PD A- allele detected was the A376G/G202A found in 12.4 % (21/170), of the children and distributed as 4.1 % (7/170) A-, 1.8 % (3/170) A-/A- homozygous deficient males and females and 6.5 % (11/170) A/A- and B/A- heterozygous deficient females. Phenotypically, 10.6 % (15/142) of the children were G6PD deficient. The asymptomatic carriage of P. falciparum by PCR was 50, 29.4, 38.2 and 38.8 % over the months of February through May 2015, respectively, and 28.8, 22.4, 25.9 and 5.9 % by microscopy during the same periods.

Conclusions

G6PD deficiency was significantly associated with a lowered risk of PCR-estimated asymptomatic P. falciparum carriage in children during the off peak malaria season in Southern Ghana.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1440-1) contains supplementary material, which is available to authorized users.

Suitability of capillary blood for quantitative assessment of G6PD activity and performances of G6PD point-of-care tests

The use of primaquine and other 8-aminoquinolines for malaria elimination is hampered by, among other factors, the limited availability of point-of-care tests for the diagnosis of glucose-6-phosphate dehydrogenase (G6PD) deficiency. Historically, the most used source of blood for G6PD analyses is venous blood, whereas diagnostic devices used in the field require the use of capillary blood; data have shown that the two sources of blood often differ with respect to hemoglobin concentration and number of red blood cells. Therefore, we have analyzed, in both capillary and venous blood drawn from the same healthy donors, the correlation of G6PD activity assessed by two qualitative tests (the Fluorescent Spot test and the CareStart test) with the gold standard quantitative spectrophotometric assay. Results obtained on 150 subjects with normal, intermediate, and deficient G6PD phenotypes show that, although differences exist between the aforementioned characteristics in capillary and venous blood, these do not impact on the quantitative assessment of G6PD activity after corrected for hemoglobin concentration or red blood cell count. Furthermore, we have assessed the sensitivity and specificity of the two qualitative tests against the gold standard spectrophotometric assay at different activity thresholds of residual enzymatic activity in both blood sources.

Performance of the CareStart glucose-6-phosphate dehydrogenase (G6PD) rapid diagnostic test in Gressier, Haiti

Administering primaquine (PQ) to treat malaria patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency can pose a serious risk of drug-induced hemolysis (DIH). New easy to use point-of-care rapid diagnostic tests are being developed as an alternative to labor-intensive spectrophotometric methods, but they require field testing before they can be used at scale. This study screened 456 participants in Gressier, Haiti using the Access Bio CareStart qualitative G6PD rapid detection test compared with the laboratory-based Trinity Biotech quantitative spectrophotometric assay. Findings suggest that the CareStart test was 90% sensitive for detecting individuals with severe deficiency and 84.8% sensitive for detecting individuals with moderate and severe deficiency compared with the Trinity Biotech assay. A high negative predictive value of 98.2% indicates excellent performance in determining those patients able to take PQ safely. The CareStart G6PD test holds much value for screening malaria patients to determine eligibility for PQ therapy.

PCR-based allelic discrimination for glucose-6-phosphate dehydrogenase (G6PD) deficiency in Ugandan umbilical cord blood

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common X-linked disorder in the world. G6PD deficiency puts children at risk for hyperbilirubinemia and kernicterus during the newborn period and an increased risk of severe hemolysis after exposure to many antimalarial medications. A laboratory diagnosis of G6PD deficiency is rare in the developing world due to limited resources. We developed a TaqMan-based allele-specific assay to rapidly determine rates of G6PD deficiency contributing alleles (G202A and A376G) in East Africa. We tested umbilical cord blood from 100 Ugandan newborns and found that the overall allele frequency of G202A was .13 and A376G was .32. The overall incidence of G6PD A- (G202A/A376G) was 6%; all A- variants were males. There was no correlation between G6PD deficiency and umbilical cord blood hemoglobin, white blood count, platelet count, or other hematologic parameters. Allele-specific PCR can serve as a rapid method to determine specific G6PD deficiency allele frequencies in a given population and as a diagnostic tool in a hospital setting in which laboratory resources are present.