SAN DIEGO – An inexpensive, rapid, and easy-to-use blood test was more than 99% accurate in detecting sickle cell disease in young children in sub-Saharan Africa, according to research reported at the annual meeting of the American Society of Hematology.
Courtesy American Society of Hematology
Dr. Erik Serrao
The test, called HemoTypeSC, uses monoclonal antibodies to detect hemoglobins A, S, and C in a drop of whole blood, said investigator Erik Serrao, PhD, of Silver Lake Research in Azusa, Calif.
Findings from the diagnostic accuracy trial, which included 1,000 children in Uganda, suggest that the immunoassay is a promising tool to enable newborn and general population screening in resource-constrained regions of high prevalence, such as Africa and India.
“Early screening plus treatment plus counseling equals saving millions of lives over the coming decades, and we believe HemoTypeSC can form an integral part of the initial part of this equation,” Dr. Serrao said during a late-breaking abstract session at the meeting.
Each test kit costs less than $2 to the end user; requires no electricity, special equipment, or training; and delivers results in about 10 minutes, he added.
Of all the late-breaking abstracts at ASH this year, the study by Dr. Serrao and his colleagues is the one with the potential to save the most lives, said Mark Crowther, MD, of McMaster University, Hamilton, Ont.
“The ability to diagnose sickle cell disease early and intervene early will result in potentially thousands of infants, who would otherwise die in infancy or early childhood, surviving into adulthood,” Dr. Crowther said during a press briefing.
Using current gold standard methods for diagnosing sickle cell disease is, at minimum, challenging and “frankly impossible” in many low-resource settings, because of the cost and the requirement for sophisticated equipment and reliable electricity, Dr. Crowther added.
In the study, investigators compared results of the HemoTypeSC test with hemoglobin electrophoresis for detection of the phenotypes HbAA (normal), HbAS (sickle cell trait), and HbSS (sickle cell disease). They compared these two testing methods in 1,000 children between the ages of 1 month and 5 years who were prospectively recruited from hospital wards and outpatient clinics in Uganda.
The immunoassay had an overall accuracy of 99.8%, correctly identifying 998 of 1,000 phenotypes as initially determined by electrophoresis. Specifically, the test correctly identified 100% of the 720 HbAA specimens, 100% of 182 HbAS specimens, and 98% of HbSS, or 96 of 98 specimens, leaving just 2 discordant samples, both of which HemoTypeSC identified as HbAS.
Investigators subsequently discovered that both of the individuals with the discordant samples had previously been diagnosed with sickle cell disease and had received recent transfusions. Both cases were subsequently confirmed as HbSS in review of previous diagnostic result reports, bringing the accuracy rate up to 100% in a secondary analysis also reported at the meeting.
Although this particular study excluded newborns, a different study of the immunoassay, recently published in the American Journal of Hematology, demonstrated 100% accuracy across multiple phenotypes in the setting of newborn screening (2018 Oct 5. doi: 10.1002/ajh.25305).
Sickle cell disease screening programs have been projected to be cost effective in Africa, Dr. Serrano said, and could even save money for governments over time as budgets are reallocated toward screening, with less money needed for treatment of patients presenting with severe complications in hospitals.
Dr. Serrao reported that he is an employee of Silver Lake Research, which funded the study, approved the study design, and donated HemoTypeSC tests.
On March 11, 2019, the editors of Blood, an ASH journal, retracted the abstract for this study. The second listed author on the abstract said that it was submitted without his consent or approval. The retraction makes no statement on the underlying science of the study, the editors noted.
This article was updated on 3/14/2019.
SOURCE: Serrao E et al. ASH 2018, Abstract LBA-3.