Pitted red cell counts in sickle cell disease. Relationship to age, hemoglobin genotype, and splenic size

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.

Severity of Anaemia Has Corresponding Effects on Coagulation Parameters of Sickle Cell Disease Patients

Sickle cell disease (SCD) is an inherited condition characterized by chronic haemolytic anaemia. SCD is associated with moderate to severe anaemia, hypercoagulable state and inconsistent platelet count and function. However, studies have yielded conflicting results with regards to the effect of anaemia on coagulation in SCD. The purpose of this study was to determine the effect of anaemia severity on selected coagulation parameters of SCD patients. Four millilitres of venous blood samples were taken from the participants (SCD and non-SCD patients) and used for analysis of full blood count and coagulation parameters. Data was analysed using SPSS version-16. From the results, it was seen that individuals with SCD had a prolonged mean PT, APTT and high platelet count compared to the controls. There was also significant difference in the mean PT (p = 0.039), APTT (p = 0.041) and platelet count (p = 0.010) in HbSS participants with severe anaemia. Mean APTT also showed significant difference (p = 0.044) with severe anaemia in HbSC participants. It can be concluded that SCD patients have prolonged PT, APTT and increased platelet count which might predispose them to bleeding episodes and thrombocytosis. Significant difference was also seen between severity of anaemia and mean PT, APTT and platelet count in HbSS individuals.

Pediatric sickle cell disease: past successes and future challenges

Once a fatal disease of childhood, more than 95% of patients born today with sickle cell disease (SCD) in developed countries are expected to survive into adulthood, largely because of improvements in supportive and preventive care (newborn screening, penicillin prophylaxis, transcranial Doppler (TCD) screening). Hydroxyurea (HU) therapy, the only oral medication currently available to prevent SCD complications, has become more widespread over the past 20 y. The NHLBI recommends that HU be offered to all patients with HbSS beginning at 9 mo of age, and the recently published Abnormal TCD with Transfusions Changing to HU (TWiTCH) trial has shown HU as an acceptable alternative to transfusion therapy for patients at high risk of stroke. While hematopoietic stem cell transplant (HSCT) is a curative option for SCD, less than 25% of patients have a suitable donor. Alternative stem cell sources from unrelated donors and haplo-identical donors are currently under investigation as are gene therapy trials. This review will focus on early efforts to elucidate SCD pathophysiology as well as supportive and preventive care improvements. Findings from recent multi-center studies (Silent Infarct Transfusion (SIT) Trial and TWiTCH) will be summarized. Finally, HSCT trials and gene therapy will be reviewed.

Plasma levels of some coagulation parameters in steady state HBSC disease patients

INTRODUCTION

Sickle cell disease is a collection of autosomal recessive genetic disorders. It includes homozygous HbSS and double heterozygote combinations such as HbSC. Central and West Africa bears a significant burden of HbSC disease.

METHODS

Prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration (FC) and platelet count (PC) were determined in 41 HbSC and HbSS patients in steady state along with 40 apparently healthy HbAA controls. One way ANOVA test was used to compare means; p values< 0.05 were considered statistically significant.

RESULTS

There was no significant difference in mean PT for the study groups (p = 0.192). Mean PC was highest in HbSS patients: 445.7 +/- 128.3 X 10 9/ L compared to HbSC: 330.0 +/- 97.7 X 10 9/ L and HbAA:245 +/- 77.7 X 10 9/ L (p = 0.000). Mean APTT was 28.1 +/- 3.8 seconds in controls,24.1 + /- 66 seconds in HbSS patients and 21.8 +/- 3.8 seconds in HbSC patients (p = 0.000). Mean FC in HbSS was 1.6 +/- 0.7 g/L, 3.2 +/- 0.6 g/L in HbSC and 2.9 +/- 0.4 g/L in HbAA (p = 0.000).

CONCLUSION

A significant difference exists in PC, APTT and FC in HbSC patients compared to HbSS patients and HbAA controls. Elevated FC and shortened APTT may play a role in complications more characteristic of HbSC such as retinopathy and osteonecrosis. These suggest HbSC is not merely a milder form of HbSS; both diseases should be seen as different entities with regards to approaches for management.

Immunocompetence of the severely injured spleen verified by differential interference contrast microscopy: the red blood cell pit test

OBJECTIVE

To determine the immunocompetence of the successfully nonoperatively managed injured spleen warranting vaccinations for overwhelming postsplenectomy sepsis by differential interference contrast microscopy (DICM).

METHODS

Cull an urban Level I trauma systems data bank for all patients with grade IV or V splenic injuries (those with the greatest potential to compromise immunologic function) successfully managed nonoperatively and those who have required splenectomies since 1996 and verify the Association for the Surgery of Trauma grading. Contact or obtain written consent of these patients and acquire a blood sample for DICM (red blood cell [RBC] pit analysis) and IgM levels (as a control). Compare values of those sustaining splenic injuries with those of two control groups: patients with splenectomies and those with normal splenic function.

RESULTS

Forty patients were contacted, consented, and volunteered blood samples: 10 patients with grade IV splenic injuries, 1 patient with a grade V injury, 14 patients with splenectomies, and 15 controls. Average RBC pit levels and IgM levels for patients sustaining injuries (15) and successfully nonoperatively managed were 0.6% (0%-2% nL) and 91 mg/dL (46-304 nL), respectively. Patients with splenectomies had levels of 20.4% and 86 mg/dL whereas controls had levels of 0.7% and 110 mg/dL, respectively. The average time frame from injury to RBC pit test was 3.1 years. Comparing the successfully nonoperatively managed group with the splenectomy group using t test with Satterthwaite's method because of unequal variances, there was a statistically significant difference (p = 0.0002). Comparing the same study group with those with normal splenic function using t test with pooled variance, there was no statistical significant difference between groups (p = 0.489).

CONCLUSION

DICM, a commonly used test to evaluate splenic-based immunocompetence in patients with sickle cell anemia, hemoglobinopathies, and patients undergoing partial splenectomies, also confirms splenic immunocompetence in patients sustaining up to grade IV splenic injuries. IgM levels earlier thought to be low in patients after splenectomy normalize.

The paradox of hemoglobin SC disease

Homozygous HbC gene results only in mild hemolytic anemia. In HbSC disease red cells contain equal levels of HbS and HbC. It is a paradox that HbSC exhibit a moderately severe phenotype in spite of being a mixture of HbS trait and HbC trait, neither of which has significant pathology. Why does the combination of these two Hbs result in a serious disease? The short answer is that HbC enhances, by dehydrating the SC red cell, the pathogenic properties of HbS, resulting in a clinically significant disorder, but somewhat milder that sickle cell anemia (SCA). Nevertheless, retinnitis proliferans, osteonecrosis, and acute chest syndrome have equal or higher incidence in HbSC disease compared to SCA. This pathogenic trick is accomplished by HbC inducing, by mechanisms not fully understood, an increase in the activity of K:Cl cotransport that induces the lost of K(+) and consequently of intracellular water. This event creates a sufficient increase of MCHC, so that the lower levels of HbS found in SC red cells can polymerize rapidly and effectively. This situation offers a unique opportunity: if we could inhibit the effect of HbC on K(+) transport we can cure the disease.

Palpable splenomegaly in children with haemoglobin SC disease: haematological and clinical manifestations

This study aimed to investigate the prevalence of palpable splenomegaly in children with haemoglobin SC (Hb SC) disease, and to determine the haematological and clinical manifestations of splenomegaly in this patient population. We performed a retrospective chart review of 100 patients with Hb SC over 2 years of age followed by the Duke University Paediatric Sickle Cell Program with serial physical examinations and laboratory measurements. Palpable splenomegaly was present in 34% of patients and was more common in males (P = 0.029). Children with splenomegaly had a significantly lower average haemoglobin concentration (10.3 vs. 10.8 g/dl, P = 0.011) and lower platelet count (237 vs. 314 x 109/l, P < 0.001) than those without splenomegaly. Children with measurements both before and after the onset of splenomegaly had a significant decrease in the platelet count (279 vs. 216 x 109/l, P < 0.001) and white blood cell count (9.1 vs. 7.9 x 109/l, P = 0.04) after splenomegaly was identified. Clinical complications included acute splenic sequestration in 12% of children (median age 5.4 years), and hypersplenism with chronic thrombocytopenia in another 10% of patients (median age 10.6 years). Splenomegaly is a common physical finding in children with Hb SC disease and is often associated with mild cytopenias. Clinical complications of splenomegaly include acute splenic sequestration in younger patients and hypersplenism with chronic thrombocytopenia in older children.

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.