5613357 ULTRASONOGRAPHIC SPLENIC INDICES AND AGE-RELATED CLINICAL AND LABORATORY PARAMETERS IN PATIENTS WITH SICKLE CELL DISEASE IN NORTH-EASTERN NIGERIA

Abstract

Background: The spleen is one of the organs affected by sickle cell disease (SCD) early in life (1-3); repeated episodes of vaso-occlusion and infarction result in a reduction in both the spleen’s structure and function (4). The rate of progression of this process varies markedly among individuals with SCD. The aim of the current study was to evaluate spleen sizes using abdominal ultrasound in children and adults with SCD in an African setting and to explore baseline clinical and laboratory variables associated with the presence or absence of the spleen. This information could be used for early monitoring and aid management among these patients. Methods: Two hundred and four sickle cell disease patients (SCD) (101 males and 103 females; age range, 1.1 to 45 years) underwent abdominal ultrasound scans at the University of Maiduguri Teaching Hospital, Nigeria between October 2020 to November 2021. One hundred and eleven age-matched healthy persons were enrolled as controls (69 males and 42 females: age range 1.5 years to 34 years). Imaging was performed by a single radiologist who assessed and measured the spleen length, depth, and width, and calculated the volume. Results: The spleen was visualized in 107 SCD patients (52.4%; 95% CI, 46% - 59%; SE 0.035) on ultrasound and was absent in 97 patients. There was a progressive increase in spleen absence with increasing age; while the spleen was present in all the under-fives, it was present in less than 24% (n = 20/85) of those 15 years and above (Fig.1). The pattern of spleen size growth with age among the SCD patients is shown in Fig.2; the median spleen length remained relatively stable at 6.5cm throughout early childhood, increasing only slightly to 7.0 cm in the 10 -14 years before reaching the adulthood size of 8.8cm from 15 years and above. Factors that were significantly associated with the presence of the spleen on the univariate analysis included high HbF and haemoglobin, low levels of platelets, HbA2, red cells indices (MCH, MCHC), positive malaria parasitemia, and history of intake of hydroxyurea. Multivariable logistic regression analysis showed only high HbF (12.2% vs 7.5%; OR, 1.17; 95% CI, 1.05 -1.29. P = 0.003) and low mean corpuscular haemoglobin concentration (MCHC) (34.1pg vs 35.1pg; OR, 0.69; 95% CI, 0.47 – 0.99. P = 0.049) were significantly associated with persistence of the spleen among SCD patients (Table 1). Only 32 (15%) patients were on regular hydroxyurea therapy, however, the HbF% level was significantly higher among patients on hydroxyurea (median 12.7; IQR 9.4) compared to their counterparts not on hydroxyurea (median 7.4; IQR 8.0) (P = 0.000). Sex and clinical parameters including frequencies of hospitalization, painful crises, febrile episodes, and total lifetime transfusion had no association with the presence of spleen on ultrasound Conclusion: In patients with SCD, the spleen persisted up to five years before any evidence of autosplenectomy occurred. Patients with persistent spleens had a higher level of HbF compared to those with absent spleens. Early determination of HbF may be of value in identifying patients who will benefit from HbF-inducing therapy such as hydroxyurea. Table 1 - Adjusted odd ratios for associations with spleen present or absent on ultrasound Parameter OR (95% Confidence interval) P value Hb, g/dl 1.07 (0.78 - 1.46) 0.675 MCH, g/dl 0.86 (0.72 - 1.02) 0.077 MCHC, pg 0.69 (0.47 - 0.99) 0.049* Platelets, ×106/µL 0.99 (0.99 -1.00) 0.274 HbF, % 1.17 (1.05 -1.29) 0.003* HbA2, % 0.75 (0.35 - 1.58) 0.447 Malaria parasite positive 2.55 (0.96 - 6.75) 0.060 Regular intake of hydroxyurea 1.84 (0.42 - 7.99) 0.418 Hb haemoglobin; MCH mean corpuscular haemoglobin; MCHC mean corpuscular haemoglobin concentration; SD standard deviation. CI con