Dagogo J. Pepple

A comparison of student performance in multiple-choice and long essay questions in the MBBS stage I physiology examination at the University of the West Indies (Mona Campus)

This retrospective study compared the performance of preclinical medical students in the multiple-choice question (MCQ) and long essay question components of a comprehensive physiology final examination. During the 3 yr analyzed, 307 students had an average score of 47% (SD 9.9) in the long essay questions and 64% (SD 9.9) in the MCQs. Regression analysis showed a significant correlation (r = 0.62, P < 0.01) between MCQs and long essay questions. When student performance was grouped by final course grade, a statistically significant correlation between MCQ and long essay scores existed only for the 210 students who received a passing grade (r = 0.20, P < 0.01). The MCQ and long essay question scores were not correlated for the 57 students who failed (r = 0.25, P = 0.06) or for the 40 students who achieved honors and distinctions (r = -0.27, P = 0.11). MCQ scores were significantly higher (P < 0.01) than essay scores for each of the groups when analyzed by two-way ANOVA. The results of this study suggest that for most students, the strong correlation between scores on MCQs and essay questions indicates that student performance was independent of testing format. For students at either end on the performance spectrum, the lack of correlation suggests that the performance in one of the testing formats had a strong influence on the final course grade. In addition, those students who failed the course were likely to be weak in both testing modalities, whereas students in all grade groups were more likely to perform better in the MCQs than in the long essay questions.

Optimal haematocrit in subjects with normal haemoglobin genotype (HbAA), sickle cell trait (HbAS), and homozygous sickle cell disease (HbSS)

The determination of an optimal haematocrit (H0) has important clinical implications if such a level can be attained, and more importantly, maintained. This is defined as a haematocrit level, above or below which oxygen delivery is deleteriously affected. This study is designed to determine an optimal haematocrit in normal (AA), sickle cell trait (AS) and sickle cell disease (SS) subjects. Twenty-seven apparently healthy subjects having normal haemoglobin genotype, 24 with sickle cell trait and 42 with homozygous sickle cell disease were recruited into the study. Whole blood viscosity (WBV) was measured by a Wells Brookfield Cone and Plate Viscometer at a shear rate of 230 sec-1. Haematocrit was determined by an AC.Tron Coulter Counter. The optimal haematocrit was calculated as the inverse of a constant, K, which was derived from the haematocrit and viscosity data. Our findings showed that the H0 varied significantly among the 3 haemoglobin genotypes, in the order AA vs SS and AS vs SS. Additionally, the data indicated an increased H0 in subjects with sickle cell trait, suggesting a possible impairment in oxygen delivery in these individuals.

Oxygen delivery index in subjects with normal haemoglobin (HbAA), sickle cell trait (HbAS) and homozygous sickle cell disease (HbSS)

Sickle cell disease is characterized by altered blood rheology due to a reduced haematocrit and a resulting lowered viscosity. Oxygen carriage, and consequently oxygen delivery, may be deleteriously affected if the haematocrit reduction is such as to limit oxygen uptake from the lungs and delivery to the tissues. The present study seeks to determine and compare the oxygen delivery index (ODI) in subjects with normal and abnormal haemoglobin genotypes. Thirty four apparently healthy subjects having normal haemoglobin genotype (AA), 27 with sickle cell trait (AS) and 50 with homozygous sickle cell disease (SS) were recruited into the study. Whole blood viscosity was measured at low and high shear rates of 23 s(-1) and 230 s(-1), respectively, using a Wells Brookfield Cone and Plate Viscometer. Haematocrit was determined using an AC.Tron Coulter Counter. The oxygen delivery index was calculated as the ratio of the haematocrit to whole blood viscosity. There was a statistically significant difference in the ODI in the SS group compared with both the AA and AS groups. There was no statistical significance in the ODI between the AA and AS groups. The ODI may be considered as a useful assessment of oxygen delivery in subjects with sickle cell disease.

Alterations in Hemorheological Determinants and Glycated Hemoglobin in Black Diabetic Patients With Retinopathy

Alterations of hemorheological determinants and glycated hemoglobin levels are prominent features of diabetic retinopathy, resulting in the increased whole-blood and plasma viscosities observed in this condition. These variables have been reported to show ethnic variations. The present study was designed to investigate the pattern of alterations in these variables and the possible influence of plasma viscosity in black diabetic retinopathy patients. Forty-two patients, who included 14 males and 28 females (mean age, 62.81 +/- 11.38 years) were studied. The control group consisted of 30 black, nondiabetic, age-matched subjects, including 10 males and 20 females. Relative plasma viscosity, plasma fibrinogen concentration, packed cell volume, and mean glycated hemoglobin were significantly higher in the diabetic subjects compared with the controls. We observed an increase in plasma viscosity in our study population, similar to those reported in previous studies for Caucasians.

Effect of cilostazol on the p50 of the oxygen-hemoglobin dissociation curve.

Cilostazol is a drug used for the treatment of intermittent claudication caused by narrowing of the blood vessels and reduced oxygen supply, characterized by intense pain in the leg when walking. This study was designed to investigate the effect of cilostazol on the P50 of the oxygen hemoglobin dissociation curve. A total of eight healthy adult subjects were studied. Blood samples (0.5 mL) from each subject were mixed with 5, 10, and 20 μL of the 0.5 mg/mL stock solution of cilostazol to give concentrations of 10, 20, and 40 µg/mL equivalent to adult doses of 50, 100, and 200 mg, respectively. The control sample had no drug added. The oxygen hemoglobin dissociation curve of each sample was plotted and the P50 determined with a Hemox-Analyzer (TCS, Medical Products Division, Southampton, PA). The mean P50 for the control samples was 28.27 ± 0.43 mm Hg. The values of the samples exposed to 10, 20, and 40 µg/mL cilostozol were 29.63 ± 0.66, 30.15 ± 0.77, and 31.66 ± 0.62 mm Hg, respectively. There was a statistically significant difference (p < 0.01) between the control and samples exposed to 40 µg/mL cilostazol. This study suggests that cilostazol caused an increase in the release of oxygen from hemoglobin as shown in the P50 values. This effect was significant at the highest concentration of 40 µg/mL.

The effect of sildenafil on the elasticity of erythrocytes in homozygous sickle cell disease

PURPOSE One of the features of homozygous sickle cell disease (HbSS) is the impaired elasticity of the erythrocyte membrane that could impede microcirculatory blood flow and cause hypoxia and tissue damage. We investigated the effect of sildenafil, a phosphodiesterase 5 (PDE5) inhibitor that inhibits the breakdown of cyclic guanosine monophosphate (cGMP) resulting in vasodilatation, on the elasticity of HbSS erythrocyte. MATERIALS AND METHODS Blood samples from ten HbSS patients in steady state was exposed to different doses (5, 10, 20, and 40 μg/mL) of sildenafil and the elasticity of the erythrocytes measured at native hematocrit with the BioProfiler. An equal number of subjects with normal hemoglobin (HbAA) served as the control group. RESULTS There was a marginal increase in elasticity with 5 μg/mL of the drug and this became significant (P<0.05) with the 10 μg/mL dose. Thereafter, gradual nonsignificant decreases were observed with the 20 and 40 μg/mL doses. A similar trend was observed for the control group. The elasticity values for the HbSS subjects at native hematocrit were significantly (P<0.05) less when compared with the corresponding concentrations for the HbAA controls. This was reversed at a corrected hematocrit of 45%. CONCLUSION The result of this study shows that sildenafil caused an initial increase in erythrocyte membrane elasticity in both HbSS and HbAA subjects, and this later decreased with increasing concentration of the drug possibly due to the dual effect of cyclic adenosine monophosphate (cAMP).

Erythrocyte Aggregation and Blood Viscosity is Similar in Homozygous Sickle Cell Disease Patients with and without Leg Ulcers

Background There is no consensus regarding the role of red blood cell (RBC) aggregation in the pathogenesis of leg ulcers (LUs) in sickle cell disease (SCD). Objectives We sought to evaluate whether the cross‐sectional determination of RBC aggregation and hematological indices were associated with the presence of LU in homozygous SCD. Methods Twenty‐seven patients with LU and 23 with no history of ulceration were recruited into the study. A laser‐assisted rotational red cell analyzer (LoRRca) was used in the determination of the aggregation index (AI), aggregation half‐time (t1/2), and the RBC aggregate strength (AMP). Hematological indices were determined using a CELL‐DYN Ruby analyzer. Whole blood viscosity (WBV) and plasma viscosity (PV) were measured using a Vilastic bioprofiler. The data were presented as means ± standard deviation or median, interquartile range. Two‐sample t‐test was used to test for associations between the AIs, WBV, and PV in patients with and without LU. Statistical significance was taken as p < 0.05. All analyses were conducted using Stata/SE v. 12.1 (StataCorp, College Station, TX). Results The AI was comparable in the group with and without ulcers (68.6, 16.7 versus 67.7, 16.9; p = 0.74); t1/2 (1.7, 1.3 versus 1.8, 1.3; p = 0.71); AMP (18.8, 14.5 versus 19.1, 13.3; p = 0.84), WBV (3.8, 1.2 versus 3.8, 0.7; p = 0.77); and the PV (1.3, 0.08 versus 1.4, 0.1; p = 0.31) and were also not statistically different between the groups of participants. Conclusion RBC aggregation and aggregate strength are not associated with leg ulceration in SCD.

The in vitro effects of sulfadoxine/ pyrimethamine and artemether/lumefantrine on the viscoelasticity of erythrocyte membrane of healthy females

Fansidar® (sulfadoxine/pyrimethamine) and Coartem® (artemether/lumefantrine) are drugs that destroy malarial parasites and also produce free radicals which cause hemolysis of malaria-parasitized erythrocytes. This study investigated the effect of these drugs on the viscoelasticity of erythrocytes of ten healthy female subjects using the BioProfiler. The concentration for each of the two drugs were determined based on the therapeutic dose as normal, half the therapeutic dose as low and double the therapeutic dose as high. For Fansidar®, the concentrations were 0.15/0.01 mg/ml (low), 0.30/0.02 mg/ml (normal) and 0.60/0.04 mg/ml (high) based on the adult therapeutic dose of 1500/75 mg of sulfadoxine/pyrimethamine in the drug combination. For Coartem®, the concentrations were 0.03/0.19 mg/ml (low), 0.06/0.38 mg/ml (normal) and 0.12/0.76 mg/ml (high) based on the adult therapeutic dose of 320/1920 mg of artermether/lumefantrine in the drug combination. There was a statistically significant (p < 0.05) decrease in viscosity, elasticity and relaxation time with Coartem® at normal and high doses. Fansidar® also showed significant (p < 0.05) reductions in these parameters only in the high dose. This suggests that Coartem® generated significant free radicals at normal and high doses, with Fansidar® only in the high dose, resulting in increased hemolysis and ultimately reduced viscoelasticity.