Developing a paper-based diagnostic test for sickle cell disease

描述（由申请人提供）：镰状细胞病（SCD）是最常见的血红蛋白病，与显著的终生发病率和过早死亡相关。在撒哈拉以南非洲，每年有20多万儿童出生时患有SCD，其中50%以上的儿童在幼儿期死亡。如果在出生后不久诊断出SCD，这些死亡大多可以通过简单和廉价的预防措施加以预防。在低收入国家，由于大量的院外分娩和传统检测方法的高昂费用，对新生儿进行普遍筛查是不切实际的。因此，迫切需要一种简单、廉价、敏感和特定的护理点（POC）设备，以便在婴幼儿首次到当地诊所就诊时对其进行检测。为了解决这一未满足的需求，我们最近开发了一种超低成本的SCD纸质测试方法。我们的测试可以通过简单的视觉解释色谱纸上混合血红蛋白（Hb）溶解度缓冲液的血滴产生的染色模式，从而实现对SCD的高度准确诊断。通过在纸质底物中运行试验并使用Hb的自然颜色进行视觉区分，我们消除了干扰传统Hb溶解度试验的因素，同时（）获得了准确区分正常，镰状性状和SCD样品的能力，（ii）减少了所需的样本量（<10 microL）， （iii）降低了每次测试的成本（< 0.03美元）和（iv）简化了结果的解释。在最近的一项临床研究中，我们对成人和1 - 12个月大的儿童进行了验证。该试验能够以100%的敏感性和特异性检测镰状血红蛋白的存在，即使对于严重贫血（[Hb]<8 g/dL）的患者，也显示出100%的阳性预测值和100%的总体诊断准确性。这个第一阶段的项目将侧重于扩大纸基SCD测试对婴儿（小于12个月）的适用性，并开发一种用于在现场部署纸基SCD测试的诊断试剂盒。我们将对测试进行优化，以提高其对HbS<20%的敏感性，并研究HbF < 50%（存在于较年幼的婴儿中）和常见的合病，如严重贫血、高脂血症、总蛋白升高和疟疾是否对测试的诊断准确性有任何影响。我们将开发一种样品制备程序，利用低成本的塑料组件来实现一次性试剂盒，确定操作条件的范围，并完成FDA批准该测试所需的研究。一个成功的诊断试剂盒的成分数量、操作次数和每次测试的成本不应超过现有的溶解性分析，并且能够检测婴儿和幼儿样本中HbS的存在，灵敏度为>80%，阳性预测值为>90%，总体诊断价值为>90%。该项目是朝着开发低成本的SCD即时诊断测试迈出的关键一步，可能对全世界成千上万婴幼儿的健康和福祉产生潜在的变革性影响。

DESCRIPTION (provided by applicant): Sickle cell disease (SCD) is the most common hemoglobinopathy associated with significant life-long morbidity and premature mortality. Over 200,000 children are born with SCD in sub-Saharan Africa annually - more than 50% of them die in early childhood. Most of these deaths could be prevented through simple and inexpensive prophylaxis if SCD was diagnosed soon after birth. Universal screening of newborns is impractical in low-income countries due to a large number of out-of-hospital births and the prohibitive cost of conventional testing methods. A simple, inexpensive, sensitive and specific point-of-care (POC) device is therefore urgently needed to enable testing infants and young children during their first visit to a local clinic. To address this unmet need, we recently developed an ultra-low-cost, paper-based test for SCD. Our test enables highly accurate diagnosis of SCD through simple visual interpretation of the pattern of the stain produced on chromatography paper by a droplet of blood mixed with hemoglobin (Hb) solubility buffer. By running the assay in a paper substrate and using the natural color of Hb for visual discrimination, we eliminated factors that interfere with conventional Hb solubility tests, while () gaining the capacity to accurately distinguish normal, sickle trait and SCD samples, (ii) reducing the required sample volume (<10 microL), (iii) lowering the per-test cost (<$0.03) and (iv) simplifying the interpretation of results. In a recent clinical study, we validated our test for adlts and children >12 months old. The test was able to detect the presence of sickling HbS with 100% sensitivity and specificity, demonstrating a positive predictive value of 100% and overall diagnostic accuracy of 100%, even for patients with severe anemia ([Hb]<8 g/dL). This Phase I project will focus on expanding the applicability of paper-based SCD test to infants (<12 months old), and developing a diagnostic kit for deploying the paper-based SCD test in the field. We will optimize the test to increase its sensitivity for HbS<20%, and investigate whether HbF>50% (present in younger infants) and common co-morbidities such as severe anemia, hyperlipidemia, elevated total protein and malaria have any effect on the diagnostic accuracy of the test. We will develop a sample preparation procedure utilizing low-cost, plastic components to enable a disposable kit, determine the range of operating conditions, and complete the studies required for regulatory approval of the test by the FDA. A successful diagnostic kit will have the number of components, number of operations, and cost per-test not to exceed those of existing solubility assays, and be able to detect the presence of HbS in samples from infants and young children with >80% sensitivity and positive predictive value and >90% overall diagnostic value. This project represents a crucial step toward the development of a low-cost, point-of-care diagnostic test for SCD that could have a potentially transformative impact on the health and well-being of tens of thousands of infants and young children worldwide.