Assessment of Rapid Diagnostic Tests Algorithms in Transfusion Medicine Setting

Background: The rapid diagnostic tests play a pivotal role in the screening of viral markers in blood qualification for transfusion in limited resource setting. Therefore, it is important to assess their analytical performances to en-sure their proper functioning. Material and Methods: We performed a cross-sectional study by successive recruitment to assess the diagnostic value of rapid diagnostic tests algorithms using ELISA as a reference test. A total of 661 blood from donors were enrolled for this study. Rapid Diagnostic Tests (RDTs) and ELISA tests were performed for each sample by a couple of double-blinded biotechnologists. Data were collected on case report form and captured in Microsoft Excel then the file was imported and analyzed using R software version 4.0.3. Results: The diagnostic accuracy for the algorithms are summarized in Table 1. For HIV-algorithm, the internal validity parameters were as follow: sensitivity (sens) 99.0% (95% CI = 97.8, 99.5); specificity (spec) 98.3% (95% CI = 90.9, 99.7); positive likelihood ratio Figure 3. At the prevalence < 5%, the NPV of the three RDTs were 99.96%, 99.99% and 99.94%. At the same prevalence, we found the following Positive Predictive Values (PPV) 70.82%, 77.59% and 37.35% for HIV-Ag/Ab RDTs, HBV-Ag RDTs and HCV-Ab RDTs algorithms, respectively. The overall areas under the received operating characteristic (ROC) curves were 98.6%, 99.2% and 99.2%; 95.9% for HIV-Ag/Ab RDTs, HBV-Ag RDTs and HCV-Ab RDTs algorithms, respectively. Conclusion: RDTs algorithms can play a pivotal role in the screening of HIV-Ab/Ag, HBs-Ag in the setting of resources limited-countries where financial and technical expertise shortages are a standard fare. However, their use for diagnostic purposes must be done with great caution and the result must necessarily be confirmed with an ELISA or molecular technique particularly for HCV-RDTs algorithm which achieved an NLR value > 0.1.


Introduction
Screening for transfusion-transmissible infections (TTI) is mandatory in any national blood transfusion program. However, it should be noted that there are no screening programs for TTI which has no limits, the exclusive safety, perceived as the formal absence of infectious risk would be difficult to reach [1]. Nevertheless, much effort has been put into developing strategies to reduce the risk of transmission of infectious agents through blood transfusion. There is a great deal of variability in screening strategies and in the choice of tests. In addition, the tests used have different sensitivities and specificities. The specificity increasing from immunochromatographic tests called rapid diagnostic tests (RDTs) to so-called molecular tests. As a result, screening strategies may differ from high-income countries to low-income countries and between different levels within the health system of the same country [2]. Despite the combination of sensitive RDTs and specific tests like ELISA, studies have shown that there is a residual risk of TTI [3] [4] [5]. This residual risk is even higher in low-income countries than in high-income countries. The molecular tests can detect viral DNA or RNA and are effective in detecting infected donors who are in a period of seroconversion [6]. However, the implementation of these tests in routine clinical laboratories encounters technical and financial difficulties due to the lack of qualified persons and the cost of equipment and infrastructure particularly in low-income countries and especially in the provinces [4]. The RDTs which are simple in use and do not need high qualified biologists, heavy equipment's and infrastructures play a pivotal role and represent an alternative way for blood screening in low-income setting [7]. The analytical performance of RDTs are

Materials and Methods
We carried out a cross-sectional assessment of RDTs algorithms analytical performances by using blood from donors from December 2016 to June 2017. The sample size was computed according to the prevalence of HBV among blood donors in our hospital (8.9%) from our previous study. By setting the precision to 5% and the 95% confidence interval (CI) to, the number of blood donors required was 661. Blood donors were selected after a medical check and were presumed to be free from apparent pathologies. Samples were taken by venipuncture at the elbow fold with the vacutainer system. About 4 ml of whole blood were collected for each donor on a dry tube with a coagulation activator and on a tube with EDTA. For HIV serology, we used the WHO-recommended testing strategy when the prevalence is low (<5%

Results
A total of 661 samples from blood donors were enrolled in this study. Out of the them, 555 (84.0%) were male and 106 (16.0%) female. The sex-ratio was 5.2.
Occasional donors represented 443 (67.0%) versus 218 (33.0%) of regular donors. The age group from 19 to 29 years was the most represented with 37.8% followed by those aged from 30 to 39 years (33.9%) and those aged from 40 years and over (26.8%). Donors aged 18 were less represented 1.5%. We did not observe a significant difference between the median of age of the donors according  Table 1.   and 37.35% for the three algorithms, respectively.

Discussion
As part of the screening of donated blood, RDTs performance should be continuously monitored to identify any variation in analytical performance that may   recruitment. Sample size was calculated according to the prevalence of HBV-Ag in blood donors according to our previews study Modibo, C., et al. [10]. The performances of the RDTs algorithms were determined by using the ELISA as a reference test. The analytical performances of RDTs algorithms and their 95% CI were evaluated using the DiagnosisMed package [11]. The ROCR package was used to plot ROC curves and nomograms [12] and the riskyR package was used for external validity of algorithms against theorical prevalence's [13]. Our study recorded 84.0% of male blood donors with a sex-ratio of 5. than those who were negative. Likewise, the average age of regular donors was significantly lower than those who were occasional donors (34.0 vs. 32.0 years; p = 0.01). As the distribution of age between subjects positive to HCV and those who were negative did not follow the normal law, we used the Mann-Whitney U-test for comparison of the median of age. We did not find a significant dif-  Also, they could be useful in diagnostic in the specific populations like prisoners, sex workers and drug abuser who exchange the needle. Univariate analysis did not found no effect of socio-demographic parameters on the three RDTs algorithms. Multivariate analysis also did not show any effect on the HIV algorithm ( Figure 4). However, the collection in the mobile cabin: odd ratio 4.2 (95% CI = 1.6, 11.9); p = 0.004 and the positive HCV coinfection: odd ratio 6.5 (95% CI =  1.4, 36.2); p = 0.03 had a positive effect on the HBV-RDTs algorithm. The age groups (19 -29 years), (30 -39 years) and ≥40 years had a slight negative effect on the HCV algorithm whereas HBS coinfection had a positive effect odd ratio 5.6 (95% CI = 1.4, 36.5); p = 0.03 ( Figure 4). Logistic regression calls for prudence in the use of the HBV-RDTs and HCV-RDTs algorithms for the screening in the setting of coinfection of HBV and HCV. RDTs algorithms can play a pivotal role in the screening of HIV-Ab/Ag, HBs-Ag in the setting of resources limited-countries where financial and technical expertise shortages are standard fare. However, their use for diagnostic purposes must be done with great caution and the result must necessarily be confirmed with an ELISA or molecular technique particular for HCV-RDTs algorithm which achieved an NLR value > 0.1.

Conclusion
RDTs algorithms can play a pivotal role in the screening of HIV-Ab/Ag, HBs-Ag in the setting of resources limited-countries where financial and technical expertise shortages are a standard fare. However, their use for diagnostic purposes must be done with great caution given their poor external validities. The result for diagnostic purpose must necessarily be confirmed with an ELISA or molecular technique particularly for HCV-RDTs algorithm which achieved an NLR value > 0.1. Their use for diagnostic purposes should be reserved in places where the prevalence of viral markers is high.