ANNALS OF IBADAN POSTGRADUATE MEDICINE
F.A. Fasola1 and A.J. Adekanmi2
Background: The spleen serves critical haematological and immunological functions in the body. However it is also the first organ to be affected by the effects of sickling in sickle cell anaemia. While the splenic size has been evaluated in sickle cell anaemia, the spleen sizes of these patients has not been associated with any specific haematological pattern.
Objectives: To determine the haematological parameters of patients with sickle cell anaemia (SCA) in relation to spleen size.
Methods: The full blood count (FBC), the irreversibly sickled cells and blood transfusion use amongst SCA patients in steady state was evaluated. Abdominal ultrasound was also performed for all patients and HbAA control for splenic size categorization.
Results: Forty patients with SCA and 22 controls with HbAA were studied with mean age of 29.28 ± 8.10 years 28.23 ± 8.14 years respectively. The mean splenic longitudinal lengths in patients and controls were 6.3 ± 4.3cm and 8.9 ± 1.5 cm respectively (p-value < .05).
The mean haematocrit and haemoglobin value were significantly lower in SCA cases than in controls (p < 0.001). Though the red cell indices were similar but the white blood cell and platelet count were significantly higher in patients than in controls.
Among SCA cases, the spleen size showed significant positive correlation with haematocrit (r = 0.371, p = 0.019) and the age at 1st transfusion (r = 0.447, p = 0.013) but significant negative correlation with MCV, MCH, MCHC and platelet count. Above 80% of patients with severe, moderate and mild autosplenectomy had been transfused compared to 25% of patients with splenomegaly.
Conclusions: Similarities in red cell indices between patients and controls suggests an identical factor influencing the red cell indices which could be genetic such as thalassemia or environmental such as iron deficiency. The negative correlation of the spleen size with red cell indices, white cell count and platelet count and positive correlation with haematocrit suggest that spleen size can be used to determine clinical course of the disease. Earlier age at first transfusion, significantly higher frequency of blood transfusion and MCHC in patients with severe autosplenectomy suggest a more severe clinical course when compared with patients with splenomegaly, normal spleen, mild and moderate autosplenomegaly.
Keywords: Sickle cell anaemia, Splenic size, Autosplenectomy, Haematological parameters
Dr. F.A. Fasola
Department of Haematology,
College of Medicine,
University of Ibadan,
Oyo State, Nigeria.
Sickle cell anaemia is characterized by hemolytic anemia and vaso-occlusion leading to acute and chronic tissue ischemia, infarction, chronic organ damage and organ dysfunction. One of the earliest organs to be affected by recurrent infarction and progressive damage is the spleen1. The spleen serves both haematological and immunological functions. Variability of haemoglobin level with splenomegaly has been documented in both peadiatric and adult sickle cell anaemia patients2,3 with few documentations on autosplenectomy. Haematological functions of the spleen includes: erythropoiesis, maturation of the reticulocyte, lymphopoiesis, reservoir of blood cells, pitting and culling function and destruction of old red cells4. The spleen presents a hypoxic, acidic and hypoglycemic environment for the erythrocytes resulting in sickled red cells due to the limited oxygen and glucose. The sickling leads to repeated infarctions of the spleen and subsequent reduction of both morphological size and function of the spleen. The splenic sizes in patients with sickle cell anaemia vary with the degree of insult it has received, thereby giving rise to a spectrum of sizes, from repeated infarction. One extreme is splenomegaly observed during infancy and early childhood, consequent to splenic sequestration or during adulthood due to increased demand on the spleen to perform its functions2,3. The other extreme is autosplenectomy which appears as a small wrinkled firm, nodular remnant following progressive atrophy due to repeated episodes of vaso-occlusion and infarction5.
The clinical and laboratory profile of patients with sickle cell anaemia are continuously being studied to understand the biology of the disease6,7. The haematological parameters are the most commonly requested investigation to determine the line of management, adjust therapy and predict outcome. The various types of SCD manifest considerable differences in haematological parameters8. These differences are further complicated by both physiological factors and acute or chronic complications. A change in the size of the spleen is a chronic complication which is postulated to affect haematological parameters and could also be associated with a unique clinical course. Paediatric patients with splenomegaly have lower mean haematocrit; retrospective analysis of their case files showed that these patients had predominantly anaemic crises while those without splenomegaly had had predominantly vaso-occlusive crises9,10. An enlarged spleen is rare in adults with sickle cell anaemia.11 Functional changes of the spleen is related to anatomic regression of the spleen11. The slower progression to atrophy is the result of a reduced tendency to sickling in vivo therefore adult sickle cell patients who retain their spleen are judged to have less severe clinical disease. However an inverse relationship between severity and autosplectomy has been reported when blood transfusion was used to determine clinical severity12. A study by Awotua-Efebo et al showed that splenomegaly is associated with poorer haematological indices whilst autosplenectomy is associated with better indices.10 The transitory anatomic size of spleen between normal and autosplenectomy are not well recognized and studied. The patients with SCA require regular monitoring and evaluation for various reasons, therefore the knowledge of changes in haematological indices of patients induced by variation in splenic size may be useful in the management of patient. Most of the local literatures relating the spleen size to the haematological parameters have been in paediatric sickle cell anaemia patients and were not related to blood transfusion requirements13,14. The spleen in sickle patients in sub Saharan Africa is believed to be different from that of sickle cell patients outside sub Saharan Africa15. Therefore there is a need to generate local data to better understand the pathogeneses of the disease in our environment. This study aims to identify the link between haematological parameters, blood transfusion history and variations in spleen size of patients with sickle cell anaemia.
This was a cross sectional study conducted amongst Sickle cell anaemia patients in steady state attending Haematology Clinic of the University College Hospital Ibadan, Nigeria. The diagnoses of patients and controls were confirmed using haemoglobin electrophoresis at alkaline pH. The controls were haemoglobin AA apparently healthy age and sex matched individuals. Ethical approval was obtained from the joint UI/UCH Ethics committee. Written and verbal consents were obtained from each participant. Consecutive patients with SCA who were in steady state were recruited into the study. The exclusion criteria were; history of blood transfusion in the last 3 months, other sickle haemoglobin phenotypes, patients on hydroxyurea and previous history of surgery. Interviewer administered questionnaire was used to collect the following information from all participant: demographic characteristics, past medical history, drugs and blood transfusion history. The medical history included clinical problem of first presentation and age at diagnosis, numbers of painful crises and hospital admissions in the last one year, number of units of blood transfused in the patient’s lifetime. None of the patients was on hydroxyurea.
Three milliliters of blood was collected from both patients and controls into ethylenediamine- tetraacetic acid (EDTA) bottle for full blood count (FBC). The sample for full blood count was analyzed immediately using sysmex autoanalyzer Kobe, Japan. The following parameters were determined; haemoglobin concentration (Hb), haematocrit (Hct), red blood cell count (RCC), mean corpuscular haemoglobin (MCH), mean cell volume (MCV), mean corpuscular haemoglobin concentration (MCHC), white cell count (WCC) and differentials, and platelet count (plt ct). The irreversibly sickled cells (ISC) were manually estimated as percentages of the total red cells enumerated from blood films made with the Leishman stain and examined under high power microscope (X100) field as described by Dacie and Lewis16. Patients were sent for abdominal ultrasound immediately samples for FBC were collected.
All SCA cases and controls were scanned using an Ultrasonix SP ultrasound machine with a 3 – 5 MHz curvilinear transducer. In the posterior axillary line in the area of the 10th rib was located and scanned through the intercostal space to have the entire the longitudinal view of the spleen with the hilus. In this position, maximum length were measured between the most superomedial and the most inferolateral points of the spleen.
Splenic sizes were determined by ultrasonographically measured craniocaudal lengths of the spleen in our subjects. In this study, we categorized splenic sizes into three groups; Splenomegaly, normal size and autosplenectomy. A splenic length of 7cm – 13 cm was regarded as normal in this study, according to the generally accepted values17,18. Autosplenectomy were splenic lengths < 6cm according to the report of Ojo et al.15 Autopslenectomy was further categorized in this study as; severe-absence of a spleen or splenic tissue less than 1cm in the absence of any history of splenectomy5,13. Moderate form was defined as the long axis of the spleen measured <1cm but less than 5.0cm (regarded as shrunken by some researchers) while Splenomegaly was defined when the long axis of the organ longer than 13.0cm17,18. Furthermore, we classified splenic lengths >5.0cm but < 6.9cm as mild splenectomy.
Data were analyzed using SPSS version 23 (Statistical Package for Social Sciences, Inc., Chicago, Ill). The descriptive data were given as means ± standard deviation (SD) for continuous variable and frequency and percentages for categorical data. ANOVA was used to determine the significance of differences in more than 2 variables. Spearman correlation was used to determine the relationship between the splenic sizes and haematological parameters. Chi square was used to determine significance among proportional variables. Logistic regression was used to determine the degree of association. The differences were considered to be statistically significant when the p value obtained was < 0.05.
Demographic and clinical characteristic of patients
A total of 40 patients with SCA and 22 apparently healthy HbA controls were recruited. The mean age of patients was 29.3 ± 8.1 years while the mean age of the controls was 28.2 ± 8.1 years. The male: female ratio for patients and controls were 1: 1.3 and 1.1:1 respectively.