Glucose-6-phosphate dehydrogenase deficiency in transfusion medicine: the unknown risks

The hallmark of glucose-6-phosphate dehydrogenase (G6PD) deficiency is red blood cell (RBC) destruction in response to oxidative stress. Patients requiring RBC transfusions may simultaneously receive oxidative medications or have concurrent infections, both of which can induce haemolysis in G6PD-deficient RBCs. Although it is not routine practice to screen healthy blood donors for G6PD deficiency, case reports identified transfusion of G6PD-deficient RBCs as causing haemolysis and other adverse events. In addition, some patient populations may be more at risk for complications associated with transfusions of G6PD-deficient RBCs because they receive RBCs from donors who are more likely to have G6PD deficiency. This review discusses G6PD deficiency, its importance in transfusion medicine, changes in the RBC antioxidant system (of which G6PD is essential) during refrigerated storage and mechanisms of haemolysis. In addition, as yet unanswered questions that could be addressed by translational and clinical studies are identified and discussed.

Use of the haematopoietic progenitor cell parameter in optimizing timing of peripheral blood stem cell harvest

BACKGROUND AND OBJECTIVES

Timing of peripheral blood stem cell (PBSC) harvest is typically based on quantification of peripheral blood (PB) CD34+ cells. CD34 enumeration is expensive, requires expertise and takes a minimum of 1-2 h to perform. The Sysmex XE2100 is an automated haematology analyser that can rapidly and inexpensively identify haematopoietic progenitor cell (HPC) populations in PB. The aim of this study was to examine if HPC can be used to optimize timing of PBSC harvest.

MATERIALS AND METHODS

White blood cell (WBC), HPC and CD34 counts were determined in a total of 60 mobilized donors. Data were analysed to examine the utility of WBC and HPC counts in predicting preharvest CD34+ counts.

RESULTS

In adults presenting for autologous collection, a PB HPC threshold of > 30/microl predicts a preharvest CD34+ count of > 20/microl with sensitivity of 86% and positive predictive value (PPV) of 100%. Among paediatric patients with a diagnosis of neuroblastoma, an HPC threshold of > 16/microl yielded sensitivity and PPV of 100%, while in children with other diagnoses, an HPC cut-off of > 44/microl yielded sensitivity and PPV of 67% and 100%, respectively. Eighty per cent of adequately mobilized allogeneic donors were identified using an HPC threshold > 15/microl, with a PPV of 100%. PB WBC can also aid in predicting CD34 counts in most patient groups, albeit with lower sensitivity than HPC.

CONCLUSION

By virtue of being a sensitive and accurate predictor of preharvest CD34+ counts, our data support the use of the HPC parameter in optimizing the timing of PBSC harvest.

Midwall fractional shortening is an independent predictor of left ventricular diastolic dysfunction in asymptomatic patients with systemic hypertension

Conventional measures of left ventricular (LV) systolic performance suggest that diastolic dysfunction precedes the development of systolic dysfunction in hypertension. Midwall fractional shortening is a new measure of systolic function that identifies hypertensive patients who have evidence of target-organ damage, impaired contractile reserve, and increased mortality. We therefore sought to determine whether depressed midwall fiber shortening is associated with abnormal diastolic function. Echocardiograms were obtained in 102 otherwise healthy hypertensive patients without treatment with normal conventional measures of systolic function. Of these, 15 had depressed midwall shortening based on previously described normative relations. Patients with depressed midwall shortening had slightly higher blood pressure. Abnormal diastolic function, defined as late (A) LV inflow velocity greater than early (E) velocity, was observed in 33% of those with normal midwall shortening but in 60% of those with depressed shortening (p <0.05). Patients with A/E >1 had lower absolute midwall fiber shortening (15 +/- 3% vs 18 +/- 3%, p <0.0001) but similar endocardial shortening. Patients with abnormal midwall shortening had higher A/E and longer isovolumic relaxation times (both p <0.05). In multivariate analysis, midwall fractional shortening, age, and heart rate were independent predictors (p <0.01) of A/E in a model including blood pressure, LV mass, and endocardial shortening. We conclude that subnormal midwall shortening predicts LV diastolic abnormalities in this population of hypertensive patients with otherwise normal measures of LV systolic function. Contrary to our previous understanding, depressed LV systolic performance, when identified with this newer method, occurs coincidentally with impaired diastolic function.

Resting diastolic function and left ventricular mass are related to exercise capacity in hypertensive men but not in women

We evaluated the impact of diastolic function and gender on exercise capacity in sedentary, untreated hypertensive subjects (34 men, 23 women) using echocardiography and a bicycle ergometry with measurement of oxygen consumption (VO2). In men, peak (A) mitral inflow velocity and left ventricular (LV) mass were inversely related to peak VO2 (r = -0.64) and maximal workload (r = -0.57) and were the sole independent determinants of exercise capacity. In women, there was no relationship between any echocardiographic measure and exercise capacity. Thus, LV mass and Doppler-determined diastolic function predict maximal VO2 in hypertensive men but not in women. This finding may be related to gender differences in the contribution of diastolic filling to exercise capacity or may reflect limitations of resting Doppler echocardiography to predict exercise diastolic filling in hypertensive women.

Deletion polymorphism of the angiotensin-converting enzyme gene is independently associated with left ventricular mass and geometric remodeling in systemic hypertension

An insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene is associated with myocardial infarction, cardiomyopathy, and left ventricular (LV) hypertrophy. LV mass and geometry are related to cardiovascular morbidity and mortality. Two-dimensional directed M-mode echocardiograms and 24-hour ambulatory blood pressure monitoring were performed in 67 hypertensive subjects. Echocardiographic measurements were assessed in blinded fashion. LV mass index and relative wall thickness were calculated. ACE genotypes were determined by polymerase chain reaction amplification of deoxyribonucleic acid prepared from leukocytes, using primers that encompass the polymorphic segment. Systolic ambulatory blood pressure was higher in subjects with the II genotype. All other patient characteristics were similar across genotype groups. After adjustment for other covariables, the DD and ID genotypes were associated with significantly higher LV mass index than was the II genotype. Adjusted relative wall thickness was also higher in subjects with the DD genotype than in subjects with the ID and II genotypes. On multiple regression analysis, systolic ambulatory blood pressure, gender, body mass index, and the ACE genotype were each independently related to LV mass index (R2 = 0.53). Systolic ambulatory blood pressure, race, and ACE genotype were each independently related to relative wall thickness (R2 = 0.34). The ACE genotype explained an additional 3% and 4% of the variations of LV mass index and relative wall thickness, respectively. In conclusion, ACE polymorphism accounted for a small but statistically significant proportion of the variation in LV mass and geometry in our hypertensive subjects.