Developing a paper-based diagnostic test for sickle cell disease

描述(申请人提供)：镰状细胞病(SCD)是最常见的与严重的终生发病率和过早死亡有关的血红蛋白病。在撒哈拉以南非洲，每年有超过20万名儿童出生时患有SCD，其中超过50%的儿童在儿童早期死亡。如果SCD在出生后不久被诊断出来，这些死亡中的大多数可以通过简单而廉价的预防措施来预防。在低收入国家，对新生儿进行普遍筛查是不切实际的，因为大量的院外分娩和传统检测方法高昂的费用。因此，迫切需要一种简单、廉价、灵敏和特定的护理点(POC)设备，以使婴儿和幼儿能够在他们第一次到当地诊所就诊时进行测试。为了解决这一未得到满足的需求，我们最近开发了一种超低成本的纸质SCD测试。我们的测试通过简单直观地解释色谱纸上由一滴血液与血红蛋白(Hb)溶解缓冲液混合产生的污渍图案，实现了对SCD的高度准确诊断。通过在纸衬底上运行分析并使用Hb的自然颜色进行视觉辨别，我们消除了干扰传统Hb溶解度测试的因素，同时()获得了准确区分正常、镰刀状和SCD样本的能力，(Ii)减少了所需的样本量(&lt；10微升)，(Iii)降低了每次测试的成本(&lt；$0.03)和(Iv)简化了结果的解释。在最近的一项临床研究中，我们验证了我们对ADLTS和12个月大的儿童的测试。该试验能够以100%的灵敏度和特异度检测病态HBs的存在，显示出100%的阳性预测价值和100%的总体诊断准确率，即使对于严重贫血([Hb]和lt；8g/dL)的患者也是如此。这个第一阶段的项目将重点扩大纸质SCD测试的适用范围到婴儿(&lt；12个月大)，并开发一种诊断试剂盒，以便在现场部署纸质SCD测试。我们将优化这项测试，以提高其对HBS&lt；20%的灵敏度，并调查HBF&gt；50%(存在于较小的婴儿中)和常见共病，如严重贫血、高脂血症、总蛋白升高和疟疾是否对该测试的诊断准确性有任何影响。我们将开发一种利用低成本塑料组件的样品制备程序，以实现一次性试剂盒，确定操作条件的范围，并完成FDA监管部门批准该测试所需的研究。一种成功的诊断试剂盒应具有不超过现有溶解度分析的组件数量、操作次数和每次测试成本，并能够检测婴儿和幼儿样本中HBS的存在，灵敏度和阳性预测值分别为80%和90%。该项目代表着朝着开发一种低成本的SCD医疗保健点诊断测试迈出的关键一步，该测试可能会对世界各地数万名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.