For decades, blood typing in Indonesia has relied on standard serological tests that categorize donors as either RhD-positive or RhD-negative. But a new study published in Transfusion suggests that for thousands of people, that label is fundamentally misleading.

Researchers investigating the molecular basis of RhD negativity in Indonesia found that approximately 15% of individuals classified as RhD-negative by routine testing actually carry the "Asian-type DEL" allele. These individuals are not truly RhD-negative; they possess a variant that produces a very low level of the RhD protein, often undetectable by standard hospital screening methods.

Why the Misclassification Matters

The implications of this discovery extend far beyond the blood bank. In clinical practice, misidentifying an Asian-type DEL carrier as RhD-negative can lead to unnecessary medical interventions or, conversely, dangerous transfusion reactions.

When a patient who is actually an Asian-type DEL carrier receives RhD-negative blood, they are generally safe. However, the real risk lies in pregnancy. If a pregnant woman is misidentified as RhD-negative, she may receive prophylactic treatment that is clinically unnecessary. More critically, if the diagnostic gap isn't closed, the medical community risks missing the nuances of hemolytic disease of the fetus and newborn (HDFN), a condition where a mother’s immune system attacks the red blood cells of her fetus.

"We strongly support the attitude of managing Asian-type DEL patients as D-positive patients," the study authors wrote. "Definitely, this practice could be made possible only by the implementation of a systematic genotyping strategy."

Beyond the Asian-Type DEL

While the prevalence of the Asian-type DEL allele—found in 64 of 436 donors analyzed—mirrors patterns seen in neighboring Thailand, the study also uncovered significant genetic diversity previously undocumented in the region.

The investigators identified five novel RHD alleles, each with different impacts on protein expression. Some, such as the RHD*1220delT variant, likely result in a truncated protein that renders the individual truly RhD-negative. Others, involving complex splice-site mutations, disrupt the genetic instructions for the RhD protein entirely.

These findings highlight the limitations of current serological testing. While 82.5% of the study participants showed a complete RHD gene deletion—the standard "true" negative—the remaining 17.5% represent a complex landscape of variants that standard hospital tests are simply not designed to see.

The Geographic Gap in Data

There is a significant caveat to these findings: the study was heavily skewed toward donors in western Indonesia. The genetic architecture of blood types in eastern Indonesia—including Papua, Maluku, and Sulawesi—remains largely a "black box."

Given the high degree of regional genetic variation, researchers suspect that eastern provinces may harbor additional, undiscovered RHD alleles. As Indonesia moves toward more precise blood banking, the need for a national genotyping strategy becomes clearer.

Key Takeaways

  • Diagnostic Discrepancy: Roughly 15% of Indonesian blood donors labeled as RhD-negative are actually carriers of the Asian-type DEL allele, which produces low levels of RhD protein.
  • Clinical Management: Experts now argue that Asian-type DEL carriers should be managed as RhD-positive to improve transfusion safety and avoid unnecessary obstetric interventions.
  • Need for Genotyping: Standard serological testing is insufficient for the Southeast Asian population; systematic molecular genotyping is required to accurately distinguish "true" RhD-negative individuals from those with variants.

As the medical community in Southeast Asia begins to integrate these findings, the focus will shift toward the feasibility of large-scale genotyping. Implementing such a system is a massive logistical undertaking, but for the safety of patients and pregnant women, it is becoming an unavoidable necessity.

This article is for informational purposes only. Always consult a qualified healthcare professional before making any medical decisions.