Clinical and laboratory features associated with persistent gross splenomegaly in Nigerian children with sickle cell anaemia

The spectrum of splenic complications in patients with sickle cell disease in Africa: a systematic review

The majority of the global population of sickle cell disease (SCD) patients resides in Africa. Individuals with this condition are at great risk of serious infections and early mortality secondary to splenic dysfunction without preventative measures. This review investigated the spectrum of splenic complications encountered in SCD among populations in Africa. We systematically searched several databases for all articles published through March 3, 2020. We included 55 studies from 14 African countries. This review reveals the difference in frequency of splenic complications in SCD in Africa when compared with their counterparts in the United State and Europe. While several studies (n = 45) described splenomegaly with a prevalence of 12% to 73% among children, and 4% to 50% among adults with HbSS, the reported prevalence for acute splenic sequestration crisis (n = 6 studies) and hypersplenism (n = 4 studies) was <10% and <5% respectively. A total of 30 surgical splenectomy was reported across eight studies. Only two (3.7%) studies provided data on spleen function. A conflicting pattern was observed amongst studies that evaluated the relationship between splenomegaly and the presence of bacterial and malaria infections. This review reveals the paucity of studies describing the role of SCD-induced splenic dysfunction in morbidity and infection related mortality in Africa.

Blood transfusion rate in Congolese patients with sickle cell anemia

OBJECTIVE

The main objective of this study was to evaluate the rate of blood transfusion in African Sickle Cell Patients and the risks related to the use of total blood.

METHODS

186 sickle cell patients (95 males and 91 females) aged 0-21 years were regularly followed over a 3 years period in Katanga province, DR Congo. Indications for blood transfusion were mainly based on clinical criteria and Hb level (less than 5g% ml or a drop of 2g% under the steady state value). All the subjects, who were transfused, wer screened for hepatitis B surface antigen (HBs Ag) and Human Immune deficit Virus (HIV).

RESULTS

Of 186 patients, 150 (80.6%) were transfused and the average blood transfusion requirement was 0.4 units per patient-year. According to the age of first transfusion, 75.3% (113/150) of them were transfused before the 6th year of life; but the frequency of transfusions seemed to decline in children aged more than 13 years. The risk of HIV infection from blood transfusion was estimated at 1 per 37.1 units or 26 per 1000 blood units. The hepatitis B surface antigen was detected in 15 cases (10%) and HIV serology was positive in 17 patients (11.3%).

CONCLUSION

Because of the complications related to blood transfusions in Africa, efforts are needed in order to reduce the frequency of transfusions, by preventive measures (early diagnosis, malarial and penicillin-prophylaxis) and to use more rational indications.

Measurement and analysis of unbound drug concentrations

The plasma protein binding of drugs has been shown to have significant effects on numerous aspects of clinical pharmacokinetics and pharmacodynamics. In many clinical situations, measurement of the total drug concentration does not provide the needed information concerning the unbound fraction of drug in plasma which is available for distribution, elimination, and pharmacodynamic action. Thus, accurate determination of unbound plasma drug concentrations is essential in the therapeutic monitoring of drugs. Many methodologies are available for determining the extent of plasma protein binding of drugs, however, in the clinical evaluation of drug therapy, equilibrium dialysis and ultrafiltration are the most routinely utilised methods. Both of these methods have been proven to be experimentally sound and to yield adequate protein binding data. Furthermore, the characterisation of the interactions between drug and protein molecules is essential for the assessment of the pharmacokinetic implications of drug-protein binding. Protein binding parameters which characterise the affinity of the drug-protein association, the number of classes of binding sites, the number of binding sites per class or protein and the binding capacity are useful for predicting unbound drug concentrations. Simple graphical methods have often been used to obtain protein binding parameters, but these methods have limitations and are not useful for drugs with more than 1 class of binding site. Therefore, the fitting of protein binding models which characterise the drug-protein binding interaction for experimental data is the preferred method of calculating binding parameters. Using the appropriate model, values for binding parameters are typically estimated by using nonlinear least-squares regression analysis.

Spleen in sickle cell anemia: comparative studies of Nigerian and U.S. patients

Anecdotal reports have attributed persistent splenomegaly in African sickle cell anemia (SS) patients to the effects of malaria. However, no comparative studies of patients in malarial and nonmalarial regions have been conducted, and few studies of malaria antibody titers have been reported. In the present study, age- and sex-matched Nigerian patients (n = 310), while it was found only in 8% of U.S. patients (n = 100) from Georgia. There was significant linear correlation between spleen size and Hb levels and with serum immunoglobulins in the Nigerian group. However, serum complement levels (C3 and C4) were not affected by spleen size. In both groups, patients with splenomegaly had fewer circulating pitted red cells than their counterparts without splenomegaly. The mean +/- SE of IgG-specific malaria antibody titer among the Nigerian patients without palpable spleens was 9,386 +/- 2,036; 9,334 +/- 2,980 in those with spleens between 1 and 5 cm, 16,201 +/- 4,502 in those with spleens between 6 and 10 cm, and 22,445 +/- 8,456 in those with spleens above 10 cm. Coexistent alpha-thalassemia did not influence the prevalence of splenomegaly among the Nigerian SS patients. This study provides additional evidence that malaria plays a significant role in the persistence of splenomegaly in African patients.