Pimlak Charoenkwan

Noninvasive prenatal diagnosis of monogenic diseases by digital size selection and relative mutation dosage on DNA in maternal plasma

Prenatal diagnosis of monogenic diseases, such as cystic fibrosis and β-thalassemia, is currently offered as part of public health programs. However, current methods based on chorionic villus sampling and amniocentesis for obtaining fetal genetic material pose a risk to the fetus. Since the discovery of cell-free fetal DNA in maternal plasma, the noninvasive prenatal assessment of paternally inherited traits or mutations has been achieved. Due to the presence of background maternal DNA, which interferes with the analysis of fetal DNA in maternal plasma, noninvasive prenatal diagnosis of maternally inherited mutations has not been possible. Here we describe a digital relative mutation dosage (RMD) approach that determines if the dosages of the mutant and wild-type alleles of a disease-causing gene are balanced or unbalanced in maternal plasma. When applied to the testing of women heterozygous for the CD41/42 (–CTTT) and hemoglobin E mutations on HBB, digital RMD allows the fetal genotype to be deduced. The diagnostic performance of digital RMD is dependent on interplay between the fractional fetal DNA concentration and number of DNA molecules in maternal plasma. To achieve fetal genotype diagnosis at lower volumes of maternal plasma, fetal DNA enrichment is desired. We thus developed a digital nucleic acid size selection (NASS) strategy that effectively enriches the fetal DNA without additional plasma sampling or experimental time. We show that digital NASS can work in concert with digital RMD to increase the proportion of cases with classifiable fetal genotypes and to bring noninvasive prenatal diagnosis of monogenic diseases closer to reality.

Prophylaxis in congenital factor VII deficiency: indications, efficacy and safety. Results from the Seven Treatment Evaluation Registry (STER)

Because of the very short half-life of factor VII, prophylaxis in factor VII deficiency is considered a difficult endeavor. The clinical efficacy and safety of prophylactic regimens, and indications for their use, were evaluated in factor VII-deficient patients in the Seven Treatment Evaluation Registry. Prophylaxis data (38 courses) were analyzed from 34 patients with severe factor VII deficiency (<1-45 years of age, 21 female). Severest phenotypes (central nervous system, gastrointestinal, joint bleeding episodes) were highly prevalent. Twenty-one patients received recombinant activated factor VII (24 courses), four received plasma-derived factor VII, and ten received freshfrozen plasma. Prophylactic schedules clustered into “frequent” courses (three times weekly, n=23) and “infrequent” courses (≤2 times weekly, n=15). Excluding courses for menorrhagia, “frequent” and “infrequent” courses produced 18/23 (78%) and 5/12 (41%) “excellent” outcomes, respectively; relative risk, 1.88; 95% confidence interval, 0.93-3.79; P=0.079. Long term prophylaxis lasted from 1 to >10 years. No thrombosis or new inhibitors occurred. In conclusion, a subset of patients with factor VII deficiency needed prophylaxis because of severe bleeding. Recombinant activated factor VII schedules based on “frequent” administrations (three times weekly) and a 90 μg/kg total weekly dose were effective. These data provide a rationale for long-term, safe prophylaxis in factor VII deficiency (clinicaltrials.gov: NCT01269138).

Hematopoietic stem cell transplantation for homozygous β-thalassemia and β-thalassemia/hemoglobin E patients from haploidentical donors

Thalassemia-free survival after allogeneic stem cell transplantation (SCT) is about 80–90% with either matched-related or -unrelated donors. We explored the use of a mismatched-related (‘haplo- ’) donor. All patients received two courses of pretransplant immunosuppressive therapy (PTIS) with fludarabine (Flu) and dexamethasone (Dxm). After two courses of PTIS, a conditioning regimen of rabbit antithymocyte globulin, Flu and IV busulfan (Bu) was given followed by T-cell-replete peripheral blood progenitor cells. GvHD prophylaxis consisted of cyclophosphamide (Cy) on days SCT +3 and +4 (post-Cy), and on day SCT +5 tacrolimus or sirolimus was started together with a short course of mycophenolate mofetil. Thirty-one patients underwent haplo-SCT. Their median age was 10 years (range, 2–20 years). Twenty-nine patients engrafted with 100% donor chimerism. Two patients suffered primary graft failure. Median time to neutrophil engraftment was 14 days (range, 11–18 days). Five patients developed mild to moderate, reversible veno-occlusive disease, while nine patients developed acute GvHD grade II. Only five patients developed limited-chronic GvHD. Projected overall and event-free survival rates at 2 years are 95% and 94%, respectively. The median follow up time is 12 months (range, 7–33 months).

Molecular and Clinical Features of Hb H Disease in Northern Thailand

Clinical assessment, hematological studies and molecular analyses were performed in 102 pediatric patients with Hb H disease in northern Thailand. A total of six mutations of the α-globin gene, which produced five genotypes, were detected. All patients had an α0-thalassemia (thal) deletion on one chromosome 16. All but one of these were of the South East Asian type (––SEA); one patient had the THAI deletion (––THAI). The deletional α+-thal mutations comprised 3.7 kb ( − α3.7) and 4.2 kb ( − α4.2) deletions which were found in 34 (33.3%) and 10 (9.8%) alleles, respectively. The nondeletional α+-thal mutations comprised 55 (53.9%) alleles of Hb Constant Spring (CS) (α142, TAA →CAA) and three (2.9%) alleles of Hb Pakse (α142, TAA→ TAT). Six patients with Hb H-CS disease also carried Hb E (AEBarts CS disease). The clinical features were diverse and the nondeletional genotypes were associated with more severe clinical and hematological features, including younger age at presentation, larger size of liver and spleen, lower hemoglobin (Hb) level, and higher transfusion requirements. The high proportion of nondeletional Hb H disease observed in this study was inconsistent with the previously reported gene frequencies of α-thal in the region, suggesting that many deletional Hb H patients with milder symptoms may have escaped recognition.

Use of cardiac markers for monitoring of doxorubixin-induced cardiotoxicity in children with cancer.

The aim of this study was to evaluate N-terminal probrain natriuretic peptides (NT-pro-BNP), cardiac troponin T, and creatinine kinase, MB isoenzyme (CK-MB) in the determination of subclinical left ventricular (LV) dysfunction by echocardiography in patients treated with doxorubicin. We performed a cross-sectional case study of systolic, diastolic function and tissue Doppler imaging by echocardiography in children with cancer who received a certain cumulative dose of doxorubicin. Blood levels for NT-pro-BNP, cardiac troponin T, and CK-MB were analyzed within 6 hours of the cardiac study. Of 30 patients, 5 (16.7%) had LV dysfunction with an abnormally high NT-pro-BNP level of 363±78 pg/mL, whereas patients with normal LV function had an NT-pro-BNP level of 148±173 pg/mL (P=0.012). The NT-pro-BNP level not only inversely correlated with fractional shortening (r=−0.43, P=0.017) and ejection fraction (r=−0.45, P=0.013) but also correlated with mitral deceleration time (r=0.41, P=0.021) and a cumulative dose of doxorubicin (r=0.44, P=0.014). For tissue Doppler imaging, NT-pro-BNP correlated with a peak systolic velocity at the myocardial segment (Sm) (r=−0.40, P=0.027). NT-pro-BNP is a sensitive test and has a moderate relationship with the LV systolic and diastolic function, thus making it a useful cardiac marker for the monitoring of early anthracycline cardiotoxicity.

Heart rate variability in beta-thalassemia patients.

Background:  Cardiac failure remains the major cause of death in beta‐thalassemia major (TM). Reduced heart rate variability (HRV) is associated with a higher risk of arrhythmias after myocardial infarction and heart failure. We evaluated HRV in TM patients and its relationship with hemodynamics and echocardiographic parameters during a 6‐month follow‐up.

Prenatal diagnosis of homozygous alpha‐thalassemia‐1 by cell‐free fetal DNA in maternal plasma

To investigate the use of cell‐free fetal DNA (cff‐DNA) to determine fetal status in pregnant women who were risk for having Hb Barts.

Cord blood screening for Α-thalassemia and hemoglobin variants by isoelectric focusing in northern Thai neonates: Correlation with genotypes and hematologic parameters

We describe the screening of newborns for thalassemia and Hb variants by using isoelectric focusing (IEF) in a population from northern Thailand where hemoglobinopathies are highly prevalent. The report focuses on findings of alpha-thalassemia, Hb E, and other hemoglobin variants, and their correlation with genotypes and hematologic parameters. Two-hundred and seven out of 566 newborns (36.6%) had thalassemia genes or Hb variants. Seventeen different genotypes were found. Nine cases (1.6%) of Hb H disease (five deletional Hb H diseases, two Hb H/Constant Spring diseases, one deletional Hb H disease/Hb E, carrier and one Hb H/Constant Spring disease/Hb E carrier) and one Hb E-beta-thalassemia were identified. IEF could clearly distinguish Hb H diseases and carriers of two alpha-globin gene defects from normal individuals according to the presence of Hb Barts and its percentage. For carriers of a single alpha-globin gene defect, Hb Barts was either absent or present in a small amount and was therefore not reliable for screening. The presence of an additional band at the Hb A(2) position in the newborns signified an Hb E carrier. One case of an absent Hb A and a presence of Hb E was identified as Hb E-beta-thalassemia. Two Hb Q-Thailand carriers were seen with two additional Hb fractions, presumably combinations of gamma-globin and beta-globin with the alpha-globin variant. Newborns with Hb H disease had lower Hb, MCV, and MCH levels than normal. MCV and MCH were also useful for differentiation of carriers of two alpha-globin gene defects, but not for carriers of Hb E or single alpha-globin gene defect. IEF was a reliable method for neonatal cord blood screening for alpha-thalassemia and Hb variants.

Outcomes of Thalassemia Patients Undergoing Hematopoietic Stem Cell Transplantation by Using a Standard Myeloablative versus a Novel Reduced-Toxicity Conditioning Regimen According to a New Risk Stratification

Improving outcomes among class 3 thalassemia patients receiving allogeneic hematopoietic stem cell transplantations (HSCT) remains a challenge. Before HSCT, patients who were ≥ 7 years old and had a liver size ≥ 5 cm constitute what the Center for International Blood and Marrow Transplant Research defined as a very high-risk subset of a conventional high-risk class 3 group (here referred to as class 3 HR). We performed HSCT in 98 patients with related and unrelated donor stem cells. Seventy-six of the patients with age < 10 years received the more conventional myeloablative conditioning (MAC) regimen (cyclophosphamide, busulfan, ± fludarabine); the remaining 22 patients with age ≥ 10 years and hepatomegaly (class 3 HR), and in several instances additional comorbidity problems, underwent HSCT with a novel reduced-toxicity conditioning (RTC) regimen (fludarabine and busulfan). We then compared the outcomes between these 2 groups (MAC versus RTC). Event-free survival (86% versus 90%) and overall survival (95% versus 90%) were not significantly different between the respective groups; however, there was a higher incidence of serious treatment-related complications in the MAC group, and although we experienced 6 graft failures in the MAC group (8%), there were none in the RTC group. Based on these results, we suggest that (1) class 3 HR thalassemia patients can safely receive HSCT with our novel RTC regimen and achieve the same excellent outcome as low/standard-risk thalassemia patients who received the standard MAC regimen, and further, (2) that this novel RTC approach should be tested in the low/standard-risk patient population.

Heart Rate Variability as an Alternative Indicator for Identifying Cardiac Iron Status in Non-Transfusion Dependent Thalassemia Patients.

Background Iron-overload cardiomyopathy is a major cause of death in thalassemia patients due to the lack of an early detection strategy. Although cardiac magnetic resonance (CMR) T2* is used for early detection of cardiac iron accumulation, its availability is limited. Heart rate variability (HRV) has been used to evaluate cardiac autonomic function and found to be depressed in thalassemia. However, its direct correlation with cardiac iron accumulation has never been investigated. We investigated whether HRV can be used as an alternative indicator for early identification of cardiac iron deposition in thalassemia patients. Methods Ninety-nine non-transfusion dependent thalassemia patients (23.00 (17.00, 32.75) years, 35 male) were enrolled. The correlation between HRV recorded using 24-hour Holter monitoring and non-transferrin bound iron (NTBI), hemoglobin (Hb), serum ferritin, LV ejection fraction (LVEF), and CMR-T2* were determined. Results The median NTBI value was 3.15 (1.11, 6.59) μM. Both time and frequency domains of HRV showed a significant correlation with the NTBI level, supporting HRV as a marker of iron overload. Moreover, the LF/HF ratio showed a significant correlation with CMR-T2* with the receiver operating characteristic (ROC) curve of 0.684±0.063, suggesting that it could represent the cardiac iron deposit in thalassemia patients. HRV was also significantly correlated with serum ferritin and Hb. Conclusions This novel finding regarding the correlation between HRV and CMR-T2* indicates that HRV could be a potential marker in identifying early cardiac iron deposition prior to the development of LV dysfunction, and may be used as an alternative to CMR-T2* for screening cardiac iron status in thalassemia patients.