Difficulties in the diagnosis of HbS/beta thalassemia: Really a mild disease?

Abstract

OBJECTIVE: HbS/β cases having clinical, hematologic and electrophoretic similarities cannot be sufficiently distinguished from sickle cell anemia cases, and are misdiagnosed as sickle cell anemia. This study will investigate the congruence between the HPLC thalassemia scanning tests and the laboratory findings in comparison with the DNA sequence analysis results of the patients diagnosed with SCA between 2016 and 2020. This study also aims to indicate the current status to accurately diagnose sickle cell anemia and HbS/β in the light of hematologic, electrophoretic and molecular studies.
 MATERIAL METHOD: Fourteen patients who were diagnosed with SCA in hospitals at different cities in Turkey and followed by the Thalassemia Diagnosis, Treatment and Research Center, Muğla Sıtkı Koçman University were included in this retrospective study. The socio demographic characteristics, hemogram, hemoglobin variant analysis results and DNA chain analysis results of the patients were taken from the database of the center and then examined. The informed consents were taken from the patients. The patients were administered a survey containing questions about transfusion history and diagnostic awareness. 
 The Beta-Thalassemia mutations were analyzed using DNA sequencer (Dade Behring, Germany) based on the Sanger method.
 RESULTS: According to the DNA sequence analysis results of these patients diagnosed with SCA in hospitals in different cities of Turkey: Of 14 patients, 8 had Hb S/β0 and Hb S/β+ and one had Hb S carrier, and one had Hb-O, and three had SCA. The patient with HbS carrier status also contains three additional mutations all of which are heterozygous. We discovered that although two of three mutations, which are c.315+16G>C and c.316-185C>T, are previously reported as benign, at least one of the two mentioned mutations, when combined with Hb S, causes transfusion-dependent Hb S/β.
 CONCLUSION: Briefly, HbSS and HbS/β thalassemia genotypes cannot be definitely characterized by electrophoretic and hematologic data, resulting in misdiagnosis. c.315+16G>C and c.316-185C>T, are previously reported as benign, at least one of the two mentioned mutations, when combined with Hb S, causes transfusion-dependent Hb S/β.
 In undeveloped or some developing countries, molecular diagnosis methods and genetic analyses cannot be used. If mutation analyses could be performed, then such differential diagnosis errors would reduce. However, if mutation analysis cannot be performed, other methods such as HPLC, capillary electrophoresis absolutely be sought to have insight into the parental carriage status.

Evaluation of the validity of the pre-marriage mean corpuscular volume value as a predictive test for b-thalassemia carrier status

“…HbA 2 is a type of hemoglobin, which plays a critical role in β-thalassemia trait screening. Noteworthy, studies have proved that the level of HbA 2 increases in β-thalassemia trait carriers while reduces sometimes, in cases with IDA and α-thalassemia trait [13] . The normal range of HbA 2 level is 2.4%–3.2%, while in β-thalassemia trait the HbA 2 level ranges between 3.6% and 7% [13] .…”

“…Noteworthy, studies have proved that the level of HbA 2 increases in β-thalassemia trait carriers while reduces sometimes, in cases with IDA and α-thalassemia trait [13] . The normal range of HbA 2 level is 2.4%–3.2%, while in β-thalassemia trait the HbA 2 level ranges between 3.6% and 7% [13] . A high HbA 2 level above or equal to 3.5% with reduced MCV and MCH values are widely reported as a typical diagnosis and valuable parameters for β-thalassemia detection [14] .…”

Scalable noninvasive amplicon-based precision sequencing (SNAPseq) for genetic diagnosis and screening of β-thalassemia and sickle cell disease using a next-generation sequencing platform

“…Approximately 10%–15% of sickle cell disease is caused by a combination of the SCD and BT mutations, also known as compound heterozygosity ( Aygun et al, 2022 ), which cannot be detected by point-of-care screening methods. The distinction between HbSS and HbS/β genotypes using current hemoglobin-based diagnostic methods can be difficult ( Chandra et al, 2017 ; Uçucu et al, 2022 ) and thus there is a need for a scalable and comprehensive genetic diagnostic method that can identify virtually all HBB mutations associated with β-hemoglobinopathies.…”

Comparison of screening indicators for different types of thalassemia carriers in Hunan Province

“…From 2018 to 2021, 1111 cases of α-thalassemia carriers, 464 cases of β-thalassemia minor and 24 cases of αβ-thalassemia were selected. The formula (RDW*RBCX*HGB)/MCV or log10 (MCH* MCHC*RDW/RBC) was evaluated for the discrimination of the two entities (thalassemia trait and iron deficiency anemia) [8] .The common screening indicators in blood routine and hemoglobin electrophoresis results were evaluated by receiver operating characteristic curve (ROC curve) and area under the curve (AUC). When AUC is greater than or equal to 0.70, the positive rate and detection rate were analyzed in combination with Youden index, specific positive rate, specific detection rate, and the appropriate cut-off value for the corresponding index was determined.…”