Evaluation of Two Serological Screening Kits for Hepatitis C Virus Infection at the Regional Blood Transfusion Center of Ouagadougou, Burkina Faso

Introduction: In Burkina Faso, screening for hepatitis C virus in blood donations is made using sensitive ELISA (Enzyme Linked Immuno Sorbent Assay) type kits. However, no confirmation of the positive results obtained with these kits is made before their notification to the blood donors due to the high costs of the confirmation kits of immunoblots type. Objective: Evaluate two rapid kits against one immunoblot kit in order to determine the most efficiency which will be proposed as an alternative for the confirmation of ELISA tests in the socio-economic context of Burkina Faso. Material and Methods: The study was carried out using a panel of 72 sera, of which 22 were positive for anti-HCV antibodies and 50 were negative. The sera were tested using the Monolisa® HCV Ag-Ab ULTRA kit and confirmed with the DECISCAN HCV Plus kit. The panel was then tested with the SD BIOLINE HCV kit and the HCV TRI-DOT kit and the results obtained were evaluated against those of the DECISCAN HCV Plus kit used as “gold standard”. Results: Compared to the DECISCAN HCV Plus kit, the HCV TRI-DOT kit ex-hibited a sensitivity and specificity of 100% and the SD BIOLINE HCV kit a sensitivity of 86.36% and a specificity of 100%. Conclusion: Based on the results recorded by the HCV TRI-DOT kit, it would be best suited to the se-How ro-epidemiological context of blood donors from the National Blood Transfusion Center and could be proposed as an alternative for confirmation of ELISA tests.


Introduction
The hepatitis C virus (HCV) is one of the major pathogens for which the world health organisation (WHO) recommends systematic screening of donated blood before any transfusion [1]. HCV infection is characterized by a long serological window (66 days) during which the virus replicates without the infected organism producing anti-HCV antibodies against it [2]. Thus, the residual risk of HCV transmission through blood transfusion would be due to this so-called silent period [2]. In order to ensure an optimal transfusion safety, WHO recommends the use of very sensitive screening kits, such as Enzyme-Linked Immu-noSorbent Assays (ELISA) in the biological qualification of blood donation [1].
Indeed, these combined antigen-antibody tests allow early detection of HCV, thus considerably reducing the residual risk linked to the serological window [3].
However, these tests turn out to be the source of a significant proportion of "false positives" results, especially with black blood donors [4]. There are several reasons for these false positives. These are in particular autoimmune diseases, viral infections, hepatic pathologies (cirrhosis), hypergammaglobulinemia, etc. [4]. These false positives not only lead to the destruction of a large quantity of blood products, the wrongful exclusion of a large number of blood donors in a context of scarcity of blood products, but also lead to stress for blood donors who find themselves in this situation. For these reasons, the results obtained by these tests require confirmation by molecular biology tests or by immunoblot type tests before blood donors are notified or before excluding them from donating blood. However, in developing countries (DCs), such confirmation is not always feasible due to the high cost of confirmatory testing.
In Burkina Faso, the management of "false positives" is all the more worrying given that HCV infection is endemic with an estimated prevalence of 3.4% [5] in the general population and 4.4% [6] among blood donors at Regional Blood Transfusion Center of Ouagadougou (RBTC/O).
Given the high-cost of the reference confirmation tests (molecular biology or immunoblot), the National Blood Transfusion Center (NBTC) of Burkina Faso uses rapid kits as an alternative to confirm the results obtained by ELISA kit of the fourth generation used in the biological qualification of blood donation.
This study aims to validate the diagnostic performances (sensitivity and specificity) of two rapid kits compared to an immunoblot kit in order to propose an

Constitution of the Panel
The samples included in the panel are serums from unpaid volunteer blood donors of both sexes aged from 18 to 60 years. Samples were collected on dry tubes from donors during blood donation, centrifuged at 4000 g for 5 minutes and collected serum were tested using the Monolisa® HCV Ag-Ab ULTRA kit

HCV TRI-DOT Kit
fourth-generation rapid visual test using the principle of immuno-filtration for the qualitative detection of HCV specific antibodies in serum or plasma. The kit contains a unique combination of modified antigens from the core, NS3, and the NS4 and NS5 regions of HCV (Table 1). These antigens are immobilized on a porous immunofiltration membrane, which includes two test points, T1 and T2, and an additional point for quality control. When the sample infiltrates through the membrane, anti-HCV antibodies present, bind to antigens immobilized on the absorbent pad. Then a conjugate is added which binds to the Fc portion of HCV-specific immunoglobulin G to give a distinct purple-pink separate dot in the test area. A color will appear at the control point after the patient's serum has been added regardless of the color that appears in the two test points (T1 and T2), confirming that the reagents are working properly and that the procedure has been followed. The test run time is 5 min.

Statistical Analyzes
The

Ethical Considerations
The informed consent of blood donors was systematically obtained before any blood donation by signing the pre-donation medical interview sheet. The study received the approval of the internal scientific review committee of the NBTC.
The anonymity and confidentiality of blood donors were respected.

Socio-Demographic Characteristics of Blood Donors Includ in the Study
A total of 72 blood donors were included in this study.

Serological Results Obtained with SD-BIOLINE HCV Kit and HCV TRI-DOT Kit
All the 50 anti-HCV antibody negative to DECISCAN HCV Plus kit included in the study were tested negative with the SD BIOLINE HCV kit and with the HCV TRI-DOT kit. Similarly, all 22 serums HCV antibody positive to DECISCAN HCV Plus kit were tested positive to HCV TRI-DOT kit (Table 3). In contrast with SD BIOLINE HCV kit, 19 serums were positive and 03 negatives. No doubtful or indeterminate results were detected by these two tests.

Performance of SD B IOLINE HCV Kit and HCV TRI-DOT Kit
Compared to the gold standard, the SD BIOLINE HCV kit has a sensitivity of 86.36% and a specificity of 100%. The HCV TRI-DOT kit showed a sensitivity and specificity of 100%. Table 4

Discussion
Our work aimed to evaluate two serologic tests for HCV infection (SD BIOLINE HCV, HCV TRI-DOT) compared to the DECISCAN HCV Plus kit to propose an alternative and inexpensive algorithm for HCV serological screening in our socio-economic context. Both tests were evaluated using a panel of serums collected from blood donors in RBTC of Ouagadougou. We chose to evaluate these two tests because they are very easy to use, provide results in less than 30 min and are less expensive, especially in resources limited contexts. They do not require highly qualified laboratory technicians, or specific laboratory equipment [7].
In addition, these kits were already present in the list of tests marketed and used in Burkina Faso for HCV screening. But, immunoblot kits such as DECISCAN HCV PLUS use enzyme-immunoassay technics and require relatively expensive laboratory equipment, reagents and relatively long handling times.
The study showed that SD BIOLINE HCV kit and HCV TRI-DOT kit both have a specificity of 100% and sensitivities of 86.36% and 100% respectively (    [8]. In the same study, Daniel et al. (2005) have also shown that this test was less sensitive to certain genotypes circulating in India including genotypes 1 and 3 [8]. However, these authors admit, as shown in our study, that HCV TRI-DOT kit provides excellent performance and competes in terms of sensitivity with ELISA kits [8].
Given the results obtained, we proposed a serological screening algorithm adapted to the socioeconomic context of Burkina Faso (Figure 3). The objective of this algorithm is to reduce as much as possible the use of confirmatory immunoblot tests while ensuring the reliability of the results. In terms of blood transfusion, the parameter sought is sensitivity because it guarantees the test's ability to detect the weakest positive samples. However, in order not to wrongly exclude donors from donating blood and also to return the results to blood donors who wish to know their serological status, it is advisable to confirm them by a test with good specificity. To do this, we have selected the HCV TRI-DOT kit with regard to its performance to offer an algorithm sequentially combining an

Conclusion
This study showed that not all commercial screening tests for HCV infection