Diagnostic accuracy of the sickle SCAN^® rapid test for neonatal screening of sickle cell disease in Lubumbashi, Democratic Republic of the Congo

Abstract

Sickle cell disease (SCD) is a common and potentially life-threatening haematological disorder. In high-income countries, universal newborn screening and timely interventions have markedly reduced infant mortality. In contrast, in low-resource settings, diagnosis often occurs only in late childhood, once clinical manifestations have developed. The high cost, technical complexity, and limited availability of conventional diagnostic methods remain major barriers to implementing neonatal screening programmes in sub-Saharan Africa and other resource-constrained regions. We assessed the diagnostic performance of Sickle SCAN®, a prototype rapid immunoassay designed to qualitatively detect HbA, HbS, and HbC. The test is based on a lateral flow immunoassay format and provides results at the point of care. Cord blood samples from 365 newborns were analysed with Sickle SCAN® and results were compared against the reference standard of capillary electrophoresis. Sickle SCAN® accurately identified haemoglobin phenotypes in 97.3% of cases (95% CI: 95.0%–98.7%). For HbAA, sensitivity was 97.8% (95% CI: 94.9%–99.3%) and specificity was 96.5% (95% CI: 92.0%–98.9%). For HbAS, sensitivity was 95.8% (95% CI: 90.5%–98.6%) and specificity 98.0% (95% CI: 95.3%–99.3%). Importantly, no false-positive or false-negative results were observed for HbSS and HbAC, yielding 100% sensitivity and specificity for these phenotypes. Our findings demonstrate that Sickle SCAN® is a highly accurate, rapid, and low-cost tool for neonatal SCD screening. Its use could substantially reduce diagnostic delays, lower programme costs, and improve accessibility to early detection in resource-limited settings, thereby contributing to improved child survival.

Introduction

Sickle cell disease (SCD) is the most common hereditary blood disorder worldwide and remains a major cause of childhood morbidity and mortality. Globally, an estimated 300,000 infants are born with SCD each year, with approximately two-thirds of these births occurring in Africa [1, 2]. The disease is characterised by chronic haemolysis, persistent inflammation, immune dysfunction, heterogeneous clinical manifestations, and progressive visceral damage. Its pathogenesis is primarily driven by chronic inflammation coupled with oxidative stress [3, 4].

The public health burden of SCD in Africa is substantial. The World Health Organization (WHO) estimates that the condition accounts for about 5% of all under-five mortality across the continent and up to 16% in countries with a particularly high prevalence [5, 6]. For example, a recent neonatal screening study in Lubumbashi reported a birth prevalence of 12.14% for sickle cell trait (HbAS) and 3.47% for sickle cell anaemia (HbSS) [7]. Overall, between 50% and 90% of children born with SCD in low-income sub-Saharan African countries are estimated to die before the age of five [8, 9], with the HbSS phenotype carrying the highest risk [10].

Early diagnosis is therefore the cornerstone of SCD management. Identifying affected infants at birth enables timely parental education and counselling, the initiation of vaccination schedules, and antibiotic prophylaxis, all of which are critical for reducing morbidity and improving survival [5, 11].

Universal newborn screening and early intervention have played a pivotal role in reducing infant mortality in high-income countries. In the United States and several other developed nations, systematic screening using highly accurate laboratory methods has enabled timely diagnosis and treatment of SCD. This approach has not only significantly reduced SCD-related infant mortality but has also contributed to improved quality of life and increased life expectancy among affected individuals [12, 13].

In contrast, in many low- and middle-income countries, SCD is frequently diagnosed only in late childhood, when clinical manifestations are already evident. The widespread implementation of neonatal screening is constrained by the high cost and complexity of conventional diagnostic techniques, which often require several days to return results [14, 15]. These methods are impractical in resource-limited settings as they demand substantial financial investment, continuous reagent supply, reliable electricity, trained laboratory personnel, and strict adherence to quality standards. Furthermore, biological samples must be transported and stored under controlled conditions, which adds to logistical challenges. Importantly, the long delay between sample collection and result delivery—sometimes exceeding 4 to 6 weeks—greatly increases the risk of loss to follow-up [16].

In recent years, point-of-care diagnostic tools have emerged as promising alternatives for simple, rapid, and reliable detection of SCD in low-resource contexts. Among these is Sickle SCAN^® (BioMedomics), a sandwich chromatographic immunoassay developed for the qualitative identification of HbA, HbS, and HbC in whole blood [17]. Previous studies conducted in different settings have demonstrated its excellent intrinsic performance for detecting common haemoglobin (Hb) variants [17–21]. However, no evaluation has yet been carried out in the Democratic Republic of the Congo (DRC), and specifically in Lubumbashi.

Although the Sickle SCAN^® test has been validated in several countries over the past decade, its evaluation in the DRC remains of particular importance. The DRC is among the countries most affected by SCD worldwide, yet systematic neonatal screening is not routinely implemented, in contrast to many high-income settings where such screening is mandatory. Introducing a simple, rapid, and affordable point-of-care test such as Sickle SCAN^® could therefore represent a crucial step toward early diagnosis and improved child survival. Furthermore, several rapid diagnostic tools for SCD currently exist, and local evidence is essential to guide national decision-makers in selecting the most appropriate tests for large-scale implementation. This study is the first evaluation of Sickle SCAN^® conducted in Lubumbashi, the second largest city in the country. By generating data from this major urban centre, our findings provide valuable insights for public health authorities seeking to design evidence-based, context-specific neonatal screening strategies across different regions of the DRC.The present study, therefore, aimed to assess the diagnostic accuracy of the Sickle SCAN^® rapid test for neonatal SCD screening in Lubumbashi, using high-performance laboratory methods as the reference standard.

Materials and methods

Study setting

The DRC is the fourth most populous country in Africa, with an estimated 105 million inhabitants distributed across 26 provinces. It is a multi-ethnic and culturally diverse nation. According to the World Bank, the DRC ranks third globally in terms of the number of people living in poverty, a situation further exacerbated by the COVID-19 pandemic. In 2018, an estimated 73% of the population—approximately 60 million people—were living on less than US$1.90 per day, the international poverty line. Consequently, nearly one in six people living in extreme poverty in sub-Saharan Africa resides in the DRC.

The Congolese health system is organised into three tiers: primary, secondary, and tertiary care. Despite significant needs, public health expenditure as a percentage of Gross Domestic Product is below the sub-Saharan African average. Household out-of-pocket payments continue to represent the main source of healthcare financing, accounting for 42% of total health expenditure in 2016 [22].

Lubumbashi, the capital of Haut-Katanga province in the south-eastern region of the DRC, is a cosmopolitan city with a population exceeding 2.5 million in 2020 and covering an area of 747 km². The dominant ethnic groups are Bemba and Luba, alongside a diversity of other Congolese communities. This study was conducted in four general referral hospitals (Katuba, Sendwe, Kamalondo, and Kenya) as well as at the University Clinics of Lubumbashi, a tertiary referral centre.

Study population, design, sample size determination, and participant selection

This was a descriptive cross-sectional study. The study population consisted of newborns less than one week old delivered in the maternity wards of the aforementioned health facilities in Lubumbashi. Eligibility for screening required prior verbal and/or written informed consent from the mother. In each health facility, two trained nurses were assigned to carry out the screening, ensuring standardized sample collection and immediate interpretation of the Sickle SCAN^® results at the point of care.

The sample size was calculated using Cochran’s formula for descriptive studies (n = z²pq/d²) [23], assuming a standard normal deviation at a 95% confidence interval (z = 1.96), an estimated prevalence of SCD of 3.47% [7], and a margin of error of 2.5% (0.025). The minimum required sample size was 206 participants. Allowing for a 20% attrition adjustment, the adjusted sample size was 248. A total of 600 newborns were initially selected for the study, and blood samples were successfully collected from 538 of them. Of these, 162 samples were excluded for technical or logistical reasons: 61 due to insufficient blood volume to perform both the Sickle SCAN^® test and capillary electrophoresis (heel-prick samples were sometimes inadequate for duplicate testing), and 101 because Sickle SCAN^® results could not be obtained following a temporary stock-out of test kits. Consequently, 376 newborns underwent parallel testing with both methods. Among these, 11 results were indeterminate (faint or unreadable bands on the Sickle SCAN^® device) and were excluded, leaving 365 valid paired results included in the final analysis (Fig. 1).

Fig. 1.

Flowchart of participants’ selection and enrolment

All newborns whose mothers provided consent between June and December 2020 were included. Newborns with a history of blood transfusion since birth were excluded.

Pre-test counselling, participant recruitment, and laboratory procedures

Before the start of the study, training sessions were provided for research assistants, laboratory technicians, and nurse counsellors. Pre-test counselling was conducted for all consenting mothers by trained nurse counsellors, and informed consent for screening was obtained from the mother of each newborn before testing.

A heel-prick blood sample (500 µL) was collected from each newborn by trained technicians into an EDTA microtainer tube. From this sample, 1–2 drops were used for the Sickle SCAN^® test (BioMedomics, Inc., Morrisville, NC, USA), a qualitative sandwich chromatographic immunoassay designed to detect human HbA, HbS, and HbC in whole blood [21]. This rapid point-of-care test reliably identifies the phenotypes HbAA, HbAS, HbAC, HbSS, HbSC, and HbCC [17, 21]. As a qualitative rather than quantitative test, Sickle SCAN^® determines only the presence or absence of HbA, HbS, and HbC. It does not detect other Hb, such as fetal Hb (HbF), which may require confirmatory testing using more advanced laboratory techniques.

The Sickle SCAN^® assay was performed immediately at the point of sample collection. Subsequently, the remaining blood samples were transported to the Monkole Hospital Centre laboratory in Kinshasa (DRC), where capillary electrophoresis was performed using a next-generation automated analyser (Capillarys 2 Flex Piercing System, Sebia SA, France). Capillary electrophoresis served as the reference method for comparison with Sickle SCAN^® in determining the accuracy of detecting HbAA (normal), HbAS (sickle cell trait), HbAC (HbC trait), HbSS (sickle cell anaemia/major sickle cell syndrome), HbSC (compound heterozygous SCD), and HbCC (haemoglobin C disease).

All Sickle SCAN^® tests were performed by trained nurses with prior experience in point-of-care diagnostic testing. They received standardised training specific to the Sickle SCAN^® assay, including sample handling, test procedure, and interpretation according to the manufacturer’s guidelines. Two independent readers, blinded to each other’s assessments, evaluated the presence or absence of bands on the Sickle SCAN^® device at the point of care immediately after sample collection, ensuring standardised and timely recording of results. The Sickle SCAN^® phenotype was classified according to the intensity of the Hb bands (Fig. 2).

Fig. 2.

Representative Sickle SCAN^® devices illustrating four common haemoglobin profiles observed in the study population

Post-test counselling

Sickle SCAN^® results were disclosed to all mothers during a same-day post-test counselling session. Confirmatory test results were subsequently communicated by telephone within one week, provided no discordant findings were observed. Children identified with SCD were referred to the paediatrician (principal investigator) for clinical follow-up and additional counselling.

Statistical analyses

All statistical analyses were conducted using Stata version 16 (StataCorp, College Station, TX, USA). For each Hb profile, the presence or absence of HbA, HbS, and HbC detected by the Sickle SCAN^® rapid test was compared against the reference standard of capillary electrophoresis. Diagnostic accuracy metrics—including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV)—were calculated, along with their 95% confidence intervals (95% CIs), using the exact Clopper-Pearson method.

Ethical considerations

Ethical approval for this study was obtained from the Medical Ethics Committee of the University of Lubumbashi (approval number: UNILU/CEM/030/2020) and conducted in accordance with the ethical principles of the Declaration of Helsinki and the national regulations of the DRC. Written informed consent was obtained from the parents or legal guardians of all newborn participants, with clear assurances of confidentiality and the right to withdraw from the study at any time without any consequences. Participants and their families were explicitly informed that involvement was entirely voluntary. The research team safeguarded the privacy of all personal data. Blood samples were collected for phenotype confirmation at no cost to participants, with all efforts made to minimise discomfort associated with venipuncture.

Results

A total of 600 newborns were initially selected, of whom 538 had blood samples collected. Among these, 376 were successfully screened with both the Sickle SCAN^® test and capillary electrophoresis over seven months (June–December 2020). After exclusion of invalid or indeterminate results, 365 valid paired results were included in the final analysis (Fig. 1). The study population consisted of 187 boys (51.2%) and 178 girls (48.8%); all participants were of Black African ancestry. The mean chronological age at screening was 0.81 days (range: 0–6 days). None of the newborns had received a blood transfusion before testing. In total, 415 newborns underwent screening for SCD using both the Sickle SCAN^® rapid test and capillary electrophoresis as the reference standard. Based on Sickle SCAN^® results, the distribution of Hb profiles was as follows: 223 (61.1%) HbAA, 120 (32.9%) HbAS, 21 (5.8%) HbSS, and 1 (0.3%) HbAC (Table 1).

Table 1.

Comparison of haemoglobin profiles identified by Sickle SCAN^®rapid test and capillary electrophoresis in newborn blood samples

Sickle SCAN®	Capillary electrophoresis
		AA	SS	AS	AC	Total
	AA	218	0	5	0	223 (61.10%)
	AS	5	0	115	0	120 (32.88%)
	SS	0	21	0	0	21 (5.75%)
	AC	0	0	0	1	1 (0.27%)
	Total	223 (61.10%)	21 (5.75%)	120 (32.88%)	1 (0.27%)	365 (100%)

Sickle SCAN^® demonstrated a diagnostic accuracy of 97.3% (95% CI: 95.0%–98.7%) in identifying Hb phenotypes. Table 2 summarises the performance of Sickle SCAN^® compared with capillary electrophoresis, the reference method. Of the 365 newborn samples analysed, Sickle SCAN^® correctly classified 355 phenotypes. Misclassification occurred in 10 cases: 4 HbAS samples were erroneously reported as HbAA, and 6 HbAA samples were incorrectly reported as HbAS.

Table 2.

Performance of the sickle SCAN^® test compared with capillary electrophoresis

Phenotype	Number	Capillary electrophoresis results	Expected results from Sickle SCAN®	Correctly tested samples	Incorrectly tested samples
Hb AA	223	A or FA	A only	218	5 (A et S)
Hb AC	1	AC	A and C	1	0
Hb AS	120	AS or FAS	A and S	115	5 (A only)
Hb SS	21	S or FS	S only	21	0
Total	365			355	10

Table 3 presents the diagnostic accuracy of Hb phenotype detection in newborns using the Sickle SCAN^® rapid test, compared with capillary electrophoresis as the gold standard. Sensitivity, specificity, PPV, and NPV, along with their 95% CIs, were calculated. For HbAA detection, sensitivity was 97.8% (95% CI: 94.9%–99.3%) and specificity was 96.5% (95% CI: 92.0%–98.9%), indicating excellent performance. Similarly, for HbAS detection, sensitivity was 95.8% (95% CI: 90.5%–98.6%) and specificity was 98.0% (95% CI: 95.3%–99.3%), also reflecting high accuracy. Notably, there were no false-positive or false-negative results for HbSS and HbAC phenotypes, yielding sensitivities and specificities of 100% (Table 3).

Table 3.

Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and corresponding 95% confidence intervals for the detection of HbA, HbS, and HbC

Phenotype	Sensitivity	Specificity	Positive predictive value	Negative predictive value
Hb AA	97.76% (94.85%-99.27%)	96.48% (91.97%-98.85%)	97.76% (94.85%-99.27%)	96.48% (91.97%-98.85%)
Hb AS	95.83% (90.54%-98.63%)	97.96% (95.30%-99.33%)	95.83% (90.54%-98.63%)	97.96% (95.30%-99.33%)
Hb SS	100.00% (83.89%-100.0%)	100.0% (98.93%-100.0%)	100.00% (83.89%-100.0%)	100.0% (98.93%-100.0%)
Hb AC	100.0% (2.50%-100.0%)	100.0% (98.99%-100.0%)	100.00% (2.50%-100.0%)	100.0% (98.99%-100.0%)

Discussion

SCD is among the most prevalent genetic disorders in the DRC. Early diagnosis remains crucial to reducing mortality associated with this condition [24]. Neonatal screening enables identification of affected infants at birth or shortly thereafter—before the onset of symptoms or complications. Early diagnosis offers a unique opportunity for close monitoring, comprehensive care, and timely interventions, which significantly reduce morbidity and mortality [14].

This study is one of the first in the DRC to evaluate the accuracy of Sickle SCAN^® in newborns compared with capillary electrophoresis, considered the gold standard. Our results demonstrate that the rapid test reliably detected HbAC and HbSS phenotypes, with near-perfect prediction for HbAS and HbAA. The overall misclassification rate was 2.74% (10/365), which is higher than the 1.1% reported in West Africa by Segbena et al. [16] but lower than the 4% reported in Paris, France, by Nguyen-Khoa et al. [21]. This discrepancy may be explained by factors such as very low Hb concentrations below the Sickle SCAN^® detection threshold, combined with persistently elevated levels of fetal Hb in newborns, both of which may interfere with diagnostic accuracy. Despite this, such a rate can be considered acceptable within a screening strategy, especially when confirmatory testing is available. Overall, these findings support the accuracy and robustness of Sickle SCAN^® in field conditions typical of low-resource settings.

Our findings are consistent with results from other countries. In a preliminary Nigerian study involving 57 adults and children, Sickle SCAN^® achieved an accuracy of 98.2% (1.8% error rate) compared with high-performance liquid chromatography [19]. Similarly, in Tanzania, Sickle SCAN^® demonstrated a sensitivity of 98.1% and a specificity of 91.1% when compared with Hb electrophoresis among 745 participants ranging in age from one day to 20 years [20]. In the United States, sensitivity ranged from 98.3% to 100% and specificity from 92.5% to 100% for detecting HbA, HbS, and HbC, again compared with capillary electrophoresis, in a cohort of 139 adults and children [18]. Taken together, these studies highlight the reliability of Sickle SCAN^® across diverse settings and populations.

Sickle SCAN^® presents several advantages over conventional laboratory methods. The test provides results within 5 min, making it particularly suitable for systematic neonatal screening programmes in resource-limited settings such as the DRC, where significant barriers include the cost of laboratory methods, inadequate infrastructure, and limited funding. Importantly, the test does not require electricity, thereby circumventing logistical challenges related to sample transport, storage, and delayed reporting [14]. This capacity for real-time communication of results is critical to ensuring prompt referral of infants with SCD to specialised care.

Furthermore, the test’s format is familiar to healthcare workers in low-resource regions, as it resembles rapid diagnostic tests already used for malaria and HIV [14, 20]. Prior research in several African countries has demonstrated that healthcare providers find Sickle SCAN^® acceptable, easy to use, and simple to interpret, with results available in under 5 min [16, 19]. Beyond its technical merits, Sickle SCAN^® also has socio-economic benefits: it is significantly less expensive (approximately US$5) compared with Hb electrophoresis (US$25), making it a cost-effective option for large-scale screening.

The introduction of rapid diagnostic tests such as Sickle SCAN^® has the potential to transform newborn screening for SCD in the DRC and similar low-resource settings. By enabling early identification and referral, such tests could help reduce the high burden of morbidity and mortality associated with SCD. Studies conducted in Bukavu have highlighted critical gaps in both healthcare workers’ knowledge and the availability of resources for SCD management, showing that only a minority of providers possess adequate training and that advanced diagnostic technologies are largely unavailable [25, 26]. Studies in Lubumbashi and Bukavu (DRC) have shown that neonatal SCD screening is feasible and generally well accepted by communities, with awareness of SCD and prior knowledge of its impact influencing willingness to participate [27, 28]. Incorporating Sickle SCAN^® into routine neonatal screening could therefore address these gaps by providing an accessible, easy-to-use, point-of-care diagnostic tool, while also fostering integration with existing maternal and child health services, including vaccination programmes and HIV prevention initiatives. From a policy perspective, scaling up neonatal SCD screening using affordable rapid diagnostics should be prioritised as part of national strategies to reduce childhood mortality, strengthen health systems, and achieve universal health coverage.

This study has certain limitations. First, the sample size, while sufficient for preliminary evaluation, may not fully capture the variability of Hb profiles across all regions of the DRC. Second, the study was conducted in urban maternity units, and families with a history of sickle cell disease may have been more likely to participate, which could have influenced the observed prevalence. Third, the study was limited to newborns, and findings may not be generalizable to older children or adults, where fetal Hb interference is less pronounced. Fourth, although capillary electrophoresis was used as the reference standard, confirmatory molecular testing (e.g., DNA analysis) was not available, which could have provided additional insights into rare Hb variants. Fifth, a small proportion of Sickle SCAN^® tests were indeterminate due to faint or unreadable bands. Finally, cost-effectiveness and feasibility analyses of large-scale implementation of Sickle SCAN^® in national programs were beyond the scope of this study and warrant further research.

Conclusion

This study demonstrates that Sickle SCAN^® is a simple, affordable, and reliable tool for neonatal screening of SCD, with sensitivity and specificity comparable to capillary electrophoresis. Its use at the community level can facilitate early diagnosis, timely referral, and initiation of comprehensive care, ultimately reducing morbidity and mortality in affected children in the DRC. Integrating this point-of-care test into national newborn screening programmes represents a critical step toward improving child health outcomes and promoting equity in healthcare delivery. While these findings are promising, further studies are needed to evaluate the feasibility, cost-effectiveness, and long-term impact of integrating Sickle SCAN^® into national newborn screening programs.

Abbreviations

95% Cis

95% confidence intervals

DRC

Democratic Republic of the Congo

Hb

haemoglobin

NPV

negative predictive value

PPV

positive predictive value

SCD

Sickle cell disease

WHO

World Health Organization

Author contributions

T.K., O.M., A.K.M., and S.O.W. conceptualised the study and designed the methodology; T.K., O.M., and O.N.L. developed the software; T.K., O.M., and S.O.W. conducted the validation; O.M., O.N.L., and S.O.W. performed formal analysis; T.K., O.M., and O.N.L. collected the data; T.K., O.M., and A.K.M. prepared the original draft of the manuscript; O.N.L., A.K.M., and S.O.W. provided supervision and contributed to the review and editing. All authors reviewed and approved the final version of the manuscript for publication.

Funding

This research received no external funding.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval for this study was obtained from the Medical Ethics Committee of the University of Lubumbashi (approval number: UNILU/CEM/030/2020) and conducted in accordance with the ethical principles of the Declaration of Helsinki and the national regulations of the DRC. Written informed consent was obtained from the parents or legal guardians of all newborn participants, with clear assurances of confidentiality and the right to withdraw from the study at any time without any consequences. Participants and their families were explicitly informed that involvement was entirely voluntary. The research team safeguarded the privacy of all personal data. Blood samples were collected for phenotype confirmation at no cost to participants, with all efforts made to minimise discomfort associated with venipuncture.

Competing interests

The authors declare no competing interests.

Consent to publish declaration.

Not applicable.

Conflict of interest

The authors declare no conflicts of interest.