Comparison of Utility and Reliability in Low-Resource Laboratory Settings of Low Cost Hemoglobinopathy Point-of-Care Screening Devices

Introduction: Many low-income countries do not have access or resources to perform newborn screening, if performed at all, with robust methods routinely used in high-resource settings such as high-performance liquid chromatography. Point-Of-Care (POC) testing methods have emerged to provide newborn screening for SCA that both reduces cost and increases access by reducing the complexity of equipment needed for testing. These include a lateral flow immunoassays (Hemotype SC™ and Sickle SCAN®), and a miniaturized electrophoresis device (Gazelle®). However, POC devices have inherent limitations including limited hemoglobin type detection, and the potential need to test samples without storage. Additionally, laboratories targeted for use of these products may be operating in conditions different from where these devices were developed, such as in areas with higher temperatures due to inconsistent electricity and air condition availability.

Methods: Discarded blood samples from pediatric patients 0-18 years old were used for testing. A total of 52 blood samples were tested, including 21 samples from infants without a known hemoglobinopathy (less than 6 months old), 19 samples from subjects with a diagnosis of Hemoglobin SS or SC disease and sickle cell trait, 2 samples from subjects with diagnosis of beta-thalassemia, 1 subject with Hemoglobin E disease, and 9 samples from subjects with no known hemoglobinopathy diagnosis. Samples were tested using a combination of the Gazelle®, Sickle SCAN® and Hemotype SC™ POC testing devices. Briefly, the Gazelle® uses a single-use disposable test cartridge to separate hemoglobin based on charge and reports out percentages of hemoglobin A, F, S, and A2/C/E. The Sickle SCAN® and Hemotype SC™ tests use a rapid, qualitative lateral flow immunoassay to detect hemoglobin A, S and C. Samples were tested using a combination of these methods then stored at different temperatures (refrigerated (3.5-3.9^oC), room temperature (20.5-20.9^oC) or incubated at 35^oC or 30^oC) and tested over different time points (24, 48, 72, and 168 hours). A chart review was also performed to determine the subject’s history including hemoglobinopathy if any, age, and prior hemoglobin electrophoresis results.

Results: Of the 21 infants without known hemoglobinopathy samples tested, the refrigerated (8) and room temperature (RT) (7) samples showed stability for up to 1 week. However, 5 out of 6 the incubated samples showed variations in results. At 48 hours, 72, and 168 hours, the Gazelle® reported hemoglobin S (10-50%) which was not seen when tested at receipt of sample. Three samples were tested using the Sickle SCAN® which showed an AS phenotype on 2 of 3 samples. For hemoglobin SC, 1 of 3 samples tested with Hemotype SC™ resulted as hemoglobin SS at all time points when refrigerated, and Sickle SCAN® and Gazelle® showed hemoglobin SC. One sample from an individual with hemoglobin E was tested using all methods which showed hemoglobin A2/C/E of 100% up to 1 week later on the Gazelle® while the Sickle SCAN® and Hemotype SC™ showed only AA phenotype.

Conclusion: Three current POC methods designed for low-cost SCA screening have varying degrees of consistency in detecting abnormal hemoglobin in different specimen storage conditions, with the Gazelle® having the most versatility in abnormal hemoglobin detection. While cheaper and somewhat easier to use, the lateral flow assays were unable to consistently identify hemoglobin C, and were unable to identify hemoglobin E, both of which were identified by the Gazelle®. When evaluating for varying temperature conditions that mimic some low-resource laboratories, all three methods showed that sample storage in warmer temperatures resulted in changes to the identified hemoglobin in the same sample. The Gazelle® also was able to consistently identify hemoglobin F, which can be useful in situations such as hydroxyurea treatment monitoring. Careful consideration should be made prior to choosing a hemoglobinopathy screening device in low-resource settings based on the suspected hemoglobin types in the population and whether hemoglobin F quantitation is needed, and samples should not have a delay in testing unless consistent refrigeration is available. Further studies are required to better understand the appropriate uses for each of these POC tests.