A Japanese multi-institutional collaborative study of antigen-positive red blood cell (RBC) transfusions in patients with corresponding RBC antibodies.

BACKGROUND AND OBJECTIVES: It is sometimes difficult to obtain antigen-negative red blood cells (RBCs) for patients with antibodies against RBCs. However, the frequency and severity of the adverse reactions have not been well elucidated. Here, we conducted a multi-institutional collaborative study to clarify the background, frequency and clinical significance of antigen-positive RBC transfusions to patients with the respective antibodies. MATERIALS AND METHODS: The survey included the background of patients, antigens on RBCs transfused, total amount of antigen-positive RBCs transfused, results from antibody screen and direct antiglobulin tests, specificity of antibodies, adverse reactions and efficacies. All antibodies were surveyed regardless of their clinical significance. RESULTS: In all, 826 cases containing 878 antibodies were registered from 45 institutions. The main reasons for antigen-positive RBC transfusions included 'negative by indirect antiglobulin test' (39%) and 'detection of warm autoantibodies' (25%). In 23 cases (3% of total), some adverse reactions were observed after antigen-positive RBC transfusion, and 25 antibodies (9 of 119 clinically significant and 16 of 646 insignificant antibodies) were detected. Non-specific warm autoantibodies were detected in 9 cases, anti-E in 5 cases, 2 cases each of anti-Lea , anti-Jra or cold alloantibodies, and 1 case each of anti-Dib , anti-Leb or anti-P1. Other antibodies were detected in 2 further cases. Five (22%) of these 23 cases, who had anti-E (3 cases) or anti-Jra (2 cases), experienced clinically apparent haemolysis. CONCLUSIONS: Adverse reactions, especially haemolysis, were more frequently observed in cases with clinically significant antibodies than those with clinically insignificant antibodies (P < 0·001).

Cut-offs for screening prolonged QT intervals from Fridericia's formula in children and adolescents.

BACKGROUND: The corrected QT interval (QTc) according to Bazett's formula (QTc = QT/RR(1/2)) has been used in clinical practice. Bazett's formula, however, overcorrects the QT interval at fast heart rates and undercorrects it at low heart rates. Guidelines and some investigators have recommended using Fridericia's formula (QTc = QT/RR(1/3)) in these cases, especially in tachycardic subjects. The aim of the present study was to determine cut-offs for QTc suitable for screening pediatric subjects with prolonged QT intervals, based on manually measured values corrected by Fridericia's formula in a large number of subjects. METHODS AND RESULTS: Three consecutive QT and RR intervals were measured in 4,655, 4,655, and 5,273 1st, 7th, and 10th graders, aged 6, 12, and 15 years, respectively. Each QT interval was corrected by Fridericia's formula, and mean values were calculated. Determination of the cut-offs for screening was based on the prevalence of abnormal electrocardiographic phenotypes of 1:1,164 and on the upper 0.025 percentile in the QTc distribution derived from previous studies. The tentative cut-offs suitable for screening subjects with prolonged QT intervals were 430 ms for 1st graders, 445 ms for 7th graders, and 440 and 455 ms for 10th grade boys and girls, respectively. CONCLUSIONS: These tentative cut-offs can be used to screen subjects with prolonged QT intervals in the clinical setting. Further studies are needed to confirm their validity.

Interval representative of transmural dispersion of repolarization in children and young adolescents with congenital long QT syndrome.

BACKGROUND: It has been shown experimentally that the interval from the nadir of the initial negative T wave to the end of the T wave is representative of transmural dispersion of repolarization (TDR) when complex T waves are present. In the clinical setting, however, the interval representative of TDR in patients with long QT syndrome (LQTS) is a controversial subject. METHODS AND RESULTS: Five symptomatic patients (3 boys, 2 girls; 3 LQT1, 2 LQT2) were evaluated by a face immersion test before and after treatment to compare the configuration of the T wave. When the notch disappeared after treatment, the single peak of the T wave after treatment coincided with the nadir of the notch before treatment. When the notch remained the same after treatment as before treatment and when the QTc decreased, the corrected interval from the nadir of the notch to the end of the T wave was for the most part shortened. CONCLUSIONS: The present study showed that the interval representative of the TDR in the clinical surface electrocardiogram can be obtained from the nadir of the notch to the end of the T wave in children and adolescents with LQTS, as was shown in the experimental study.