Journal of Applied Hematology

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 9  |  Issue : 3  |  Page : 91--94

Utility of paper-based sickle cell test compared to sodium metabisulfite sickling test using hemoglobin electrophoresis as a gold standard at Bugando Medical Center, Mwanza


Neema N Mkocha1, Erius Tebuka1, Emmanuela E Ambrose2, Betrand Msemwa1, Vitus Silago3,  
1 Department of Hematology, Weill Bugando School of Medicine, Catholic University of Health and Allied Sciences–Bugando, Mwanza, Tanzania
2 Department of Paediatrics, Weill Bugando School of Medicine, Catholic University of Health and Allied Sciences–Bugando, Mwanza, Tanzania
3 Department of Microbiology and Immunology, Weill Bugando School of Medicine, Catholic University of Health and Allied Sciences–Bugando, Mwanza, Tanzania

Correspondence Address:
Mr. Betrand Msemwa
Department of Hematology, Weill Bugando School of Medicine, Catholic University of Health and Allied Sciences-Bugando, Mwanza
Tanzania

Abstract

BACKGROUND: Sickle cell disease (SCD) describes a group of inherited red blood cell disorders. People with SCD have abnormal haemoglobin (Hb), called Hb S. In all forms of SCD, at least one of the two abnormal genes causes a person's body to make Hb S. In countries with limited resources, diagnostic technique should be simple and easy to perform with high sensitivity and specificity. METHODS: This study compared the paperbased sickle cell test and sodium metabisulfite sickling test using Hb electrophoresis as a gold standard. It was a crosssectional hospitalbased study which was conducted from July to October 2017 involving a total of 140 blood samples of under 10 years children presumed to have SCD. Blood samples in ethylenediaminetetraacetic acid anticoagulantcontaining vacutainers were used for SCD diagnosis by using paperbased and sodium metabisulfite sickling tests then confirmed by Hb electrophoresis as the gold standard. RESULTS: Blood specimens were from individuals aged 4 years ranged from 2 to 9 years. Slightly majority of blood specimens belonged to males, 54.3% (76/140) while the majority was from inpatients, 82.9% (116/140). Paperbased sickle cell test identified 46/140 (32.9%) Hb AA, 81/140 (57.9%) Hb, and 6/140 (4.3%) Hb AS. Sickling test identified 50/140 (35.7%) Hb AA and 87/140 (62.1%) Hb SS. Hb electrophoresis identified 50/140 (35.7%) Hb AA, 83/140 (59.3%) Hb SS, and 7/140 (5%) Hb AS. The paperbased sickle cell test had a sensitivity of 97.8% and specificity of 96.7% while the sickling test had the sensitivity of 96.7% and specificity of 100%. CONCLUSION: Paperbased sickle cell test was able to detect sickle cell carriers, Hb AS and shown high sensitivity and specificity; therefore, it can be used as a substitute for sickling test in countries with limited resource. However, paperbased sickle test is suitable for adults' population.



How to cite this article:
Mkocha NN, Tebuka E, Ambrose EE, Msemwa B, Silago V. Utility of paper-based sickle cell test compared to sodium metabisulfite sickling test using hemoglobin electrophoresis as a gold standard at Bugando Medical Center, Mwanza.J Appl Hematol 2018;9:91-94


How to cite this URL:
Mkocha NN, Tebuka E, Ambrose EE, Msemwa B, Silago V. Utility of paper-based sickle cell test compared to sodium metabisulfite sickling test using hemoglobin electrophoresis as a gold standard at Bugando Medical Center, Mwanza. J Appl Hematol [serial online] 2018 [cited 2019 Mar 25 ];9:91-94
Available from: http://www.jahjournal.org/text.asp?2018/9/3/91/244539


Full Text

 Introduction



Sickle cell disease (SCD) describes a group of inherited red blood cell disorders.[1],[2],[3] People with SCD have abnormal haemoglobin (Hb), called Hb S or sickle Hb, in their red blood cells.[4],[5] People who have SCD inherit two abnormal Hb genes, one from each parent.[6] In all forms of SCD at least one of the two abnormal genes causes a person's body to make Hb S.[7],[8] When a person has two Hb S genes, Hb SS, the disease is called sickle cell anemia and a person with one Hb S gene, Hb AS, is called a carrier. SCD is the most severe kind of disease among children.[2],[9],[10],[11] Characteristic features of this disorder are anemia, repeated infections, and a periodic episode of pain, the severity of symptoms varies from person to person.[12],[13] Some people have mild symptoms, whereas others are frequently hospitalized for more serious complications.[12],[14],[15],[16]

There are documented and approved tests for diagnosis of SCD including; paper-based sickle cell test, sickledex, peripheral blood film, and sodium metabisulfite sickling test, to mention few.[17] Paper-based sickle cell test method of diagnosis has been documented to be a useful screening test for SCD with high sensitivity and specificity.[18],[19] The test has also been documented to be very cheap, safe, time effective, easy to interpret, and it can differentiate SCD from sickle cell carrier compared to other screening tests like sodium metabisulfite sickling test.[18] The study conducted at Tulane University Hospital and the Sickle Cell Center of Southern Louisiana concluded that the paper-based SCD test was able to detect the presence of any HbS in a sample with a mean sensitivity of 100% and specificity of 100%.[20]

This study determined the utility of paper-based sickle cell test and sodium metabisulfite sickling test in the diagnosis of SCD as compared to Hb electrophoresis as the gold standard at Bugando Medical Center (BMC), Mwanza, Tanzania.

 Methods



This cross-sectional study was conducted between July and October 2017. A total of 140 children's blood specimens presumed to have SCD brought in ethylenediaminetetraacetic acid (EDTA) vacutainers for SCD diagnosis by using sickling test were also used for paper-based test at BMC, Central Pathology Laboratory in Mwanza, Tanzania. This study was given ethical clearance numbers; CREC 398/2017.

Laboratory procedures

Blood specimens were processed according to specific analysis' procedures as per the laboratory's standard operating procedures adhering to good clinical laboratory procedures. Paper-based sickle cell test and sodium metabisulfite sickling test were performed to diagnose SCD, and Hb electrophoresis was used as a confirmatory and cold standard technique.

Paper-based sickle cell test was performed by diluting of one part of blood samples with 10 parts of hemoglobin solubility buffer by volume. Moreover then 20 μL of the diluted blood samples were dropped onto chromatographic paper and results were interpreted [Figure 1] as previously documented.[21],[22] Sodium metabisulfite sickling test was performed on microscopic glass slides after mixing of blood samples with 2% freshly prepared sodium metabisulfite as documented previously.[23] Sickle cell shaped red blood cells under microscopic examination interpret positive results [Figure 2]. Hb electrophoresis was used to confirm results obtained by paper-based sickle cell test and sodium metabisulfite sickling test. By using normal and sickle cell blood controls, the type of blood samples Hb were determined as reported.[24],[25]{Figure 1}{Figure 2}

 Results



Basic information of blood specimens used

A total of 140 blood specimens in EDTA tubes were enrolled. Of these, 45.7% (64/140) blood specimens were from females, and 54.3% (76/140) blood specimens were from males. The median age was 4 years; ranged from 2 to 9 years. Out of 140 blood specimens, 82.9% (116/140) were from in-patient departments, and 17.1% (24/140) were from out-patient departments. 44.3% (62/140) blood specimens belonged to patients from Ilemela district, 28.6% (40/140) Nyamagana district and 40 (28.6%) other districts in Mwanza and neighboring regions [Table 1].{Table 1}

Hemoglobin electrophoresis results

Hb electrophoresis detected 35.7% (50/140) blood samples with Hb AA, blood samples with normal Hb; 59.3% (83/140) samples with Hb SS, blood samples with SCD, and 5% (7/140) samples with Hb AS, blood samples with sickle cell trait (SCT).

Paper-based sickle cell results compared to hemoglobin electrophoresis

Paper-based Hb electrophoresis identified 46/140 (32.9%) blood samples with Hb AA, 81/140 (57.9%) blood samples with Hb SS, and 6/140 (4.3%) Hb AS. The paper-based sickle cell test had sensitivity and specificity of 97.8% and 96.7%, respectively [Table 2].{Table 2}

Sickling test results compared to hemoglobin electrophoresis

The sickling test identified 50/140 (35.7%) blood samples with Hb AA and 87/140 (62.1%) blood samples with Hb SS. The sickling test had the sensitivity and specificity of 96.7% and 100%, respectively [Table 2].

 Discussion



The current study was performed to determine the utility of paper-based sickle cell test and sodium metabisulfite sickling test in the diagnosis of SCD among blood specimens of <10 years children presumed to have SCD. Hb electrophoresis, a gold standard technique, determined 59.3% SCD, and 5% SCT among blood specimens used. Compared to Hb electrophoresis, paper-based sickle cell test had a sensitivity of 97.8% and specificity of 96.7% while sodium metabisulfite sickling test had a sensitivity of 96.7% and specificity of 100% in detecting of SCD, respectively. About the same results on paper-based sickle cell test were documented in a study performed in Angola shown that the test had a sensitivity of 94.2% and specificity of 97.7%.[20] Another study conducted at Indianapolis concluded that the sensitivity and specificity of sodium metabisulfite sickling test was 97% and 99.9%, respectively, similarly to this study's results.[26]

The paper-based sickle cell test reported two false-negative results which may be due to severe anemia as the two blood specimens had the Hb levels of 6 g/dl and 4 g/dl, respectively. The presence of four false-positive results can be caused by a marked hypergammaglobilinemia or the presence of other Hb variants; this has been stated previously.[27] However, the presence of false positives may also be attributed to the presence of other proteins which are soluble in the buffer giving it the appearance of Hb A, as observed previously.[26]

Sodium metabisulfite sickling test in the current study identified four false positive samples with SCD this may be due to anemic blood samples as previously reported.[17] However, the sodium metabisulfite sickling test had a specificity of 100% as previously reported[26] is making it a reliable screening test for SCD.

This study found no benefit of paper-based sickle cell test over sodium metabisulfite sickling test in detecting of SCD using Hb electrophoresis as a confirmatory gold standard technique. Both techniques, paper-based sickle cell test and sodium metabisulfite sickling test showed a limitation in the screening of SCD on anemic blood samples. Paper-based sickle cell test has it demerit compared to sodium metabisulfite sickling test as gave false negative results in the screening of SCD, it may be employed in countries with limited resources. For this technique is easy and simple to perform with very short period of turnaround time, requiring no electricity or microscope to perform and easy to interpret. Furthermore, paper-based sickle cell technique has an advantage over sodium metabisulfite sickling test as it can differentiate SCD from SCT. However, paper-based sickle cell test is not recommended for screening of SCD in neonates due to fetal Hb which is detected as normal Hb giving false negative results.[18] With these numerous shortcomings of paper-based sickle cell test, in countries with adequate resources, sodium metabisulfite sickling test is recommended.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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