{
  "slug": "bone-marrow-match-failure",
  "question": "What are the odds of not finding a bone marrow donor match?",
  "category": "health",
  "no_reliable_estimate": false,
  "perceived": {
    "description": "Most people who have not personally needed a bone marrow transplant assume the registry system works like a blood bank — show up, get matched, receive a transplant. The reality of HLA matching, where doctors need to align 8 to 10 of 12 genetic markers, is poorly understood. The perception gap runs in both directions depending on the audience: white patients tend to underestimate the difficulty because the registry was built around donors who look like them, while patients from minority communities often learn the hard way that their match probability is dramatically lower. Public awareness campaigns have improved since the early 2000s, but the structural inequity remains largely invisible to the general public.\n",
    "rough_estimate": "Most people assume a match can be found for anyone who needs one",
    "kind": "intuition"
  },
  "native": {
    "display": "~75% match likelihood for White patients; ~29% for Black patients (8/8 HLA match)",
    "numerator": 29,
    "denominator": 100,
    "unit": "match probability for Black patients seeking 8/8 HLA match",
    "population": "US patients searching NMDP registry"
  },
  "normalized": {
    "lifetime_us_adult": 0.42,
    "display": "~42% of patients who need a transplant fail to find an optimal 8/8 HLA-matched unrelated donor (conditional on needing a transplant)",
    "log_value": -0.38,
    "assumptions": "The NEJM 2014 study by Gragert et al. estimated match likelihoods by race/ethnicity in the US registry. The population-weighted average failure rate for an 8/8 HLA match is roughly 42%, heavily skewed by the low match rates for Black (71% failure), Hispanic (48% failure), and multiracial (71% failure) patients vs White (7% failure). This is a per-search probability, not a cumulative lifetime figure, but it represents the reality facing any patient who needs an unrelated donor transplant.\n",
    "uncertainty": {
      "low": 0.25,
      "high": 0.71
    },
    "scope": "subgroup_lifetime"
  },
  "sources": [
    {
      "url": "https://www.nejm.org/doi/full/10.1056/NEJMsa1311707",
      "title": "HLA Match Likelihoods for Hematopoietic Stem-Cell Grafts in the U.S. Registry",
      "publisher": "New England Journal of Medicine",
      "source_type": "primary_study",
      "statistic": "8/8 HLA match probability: 75% White, 46% Hispanic, 42% Asian, 29% Black; registry composition is 74% White donors",
      "excerpt": "\"The probability of finding a match within the NMDP registry is estimated to be 0.93 for Whites, 0.82 for Hispanics, 0.77 for Asian Americans and 0.58 for Blacks when considering 7/8 matches. For 8/8 HLA matches, the probability is 0.75 for Whites, 0.46 for Hispanics, 0.42 for Asian Americans, and 0.29 for Blacks.\"\n",
      "source_date": "2014-07-24",
      "source_accessed": "2026-04-18",
      "archive_url": "http://web.archive.org/web/20250503110101/https://www.nejm.org/doi/full/10.1056/NEJMsa1311707",
      "calculation_notes": "Gragert et al. analyzed HLA haplotype frequencies in the NMDP registry against patient need. The 8/8 match is the clinical gold standard for unrelated donor transplant. The racial disparity arises from two compounding factors: (1) greater HLA diversity in populations of African and mixed ancestry, requiring a larger pool to find any given match, and (2) underrepresentation of minority donors in the registry (74% White at time of study). The normalized figure uses a population-weighted average across US racial demographics.\n"
    },
    {
      "url": "https://www.nmdp.org/en/get-involved/join-the-registry/ethnicity-and-diversity-matter",
      "title": "Why Ethnicity Matters for Bone Marrow Transplants",
      "publisher": "NMDP (formerly Be The Match)",
      "source_type": "reputable_reference",
      "statistic": "71% of Black patients, 71% of multiracial patients, 52% of Latino/Hispanic patients, and 53% of Asian American patients lack a perfectly matched donor in the worldwide registry",
      "excerpt": "\"71% of Blacks, 71% of multi-racial individuals, 52% of Latinos and Hispanics, and 53% of Asian Americans do not have a perfectly matched donor in the worldwide registry. A patient's ethnic background is important in predicting the likelihood of finding a match because HLA is inherited.\"\n",
      "source_date": "2025-01-01",
      "source_accessed": "2026-04-18",
      "archive_url": "http://web.archive.org/web/20260207233229/https://www.nmdp.org/en/get-involved/join-the-registry/ethnicity-and-diversity-matter",
      "calculation_notes": "NMDP's current diversity page updates the Gragert et al. data with more recent registry composition. The figures are broadly consistent with the 2014 NEJM study, suggesting that despite recruitment efforts, the structural gap has not closed substantially. The registry now includes over 22 million donors worldwide but remains majority White.\n"
    },
    {
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC3848311/",
      "title": "Racial disparities in hematopoietic cell transplantation in the United States",
      "publisher": "PMC / Bone Marrow Transplantation",
      "source_type": "peer_reviewed",
      "statistic": "Black patients are less likely to proceed to transplant and have worse outcomes, partly due to lower match availability and longer search times",
      "excerpt": "\"Whites constitute nearly 6.5 million (74%) donors in the registry, whereas the representation of Hispanics (10%), Blacks (7%) and Asians (7%) is less frequent. This underrepresentation compounds the biological challenge of greater HLA diversity in non-White populations.\"\n",
      "source_date": "2013-11-01",
      "source_accessed": "2026-04-18",
      "archive_url": "https://web.archive.org/web/20260420032419/https://pmc.ncbi.nlm.nih.gov/articles/PMC3848311/",
      "calculation_notes": "This review contextualizes the match-rate disparity within the broader transplant pipeline. Lower match probability leads to longer search times, which leads to disease progression, which leads to worse outcomes or ineligibility for transplant. The disparity is not purely a registry-size problem — HLA diversity means that even a proportionally representative registry would yield lower match rates for Black patients unless the registry were substantially larger overall.\n"
    }
  ],
  "comparison_anchors": [
    {
      "label": "Blood type compatibility for transfusion (O-negative universal)",
      "lifetime_us_adult": 0.93
    },
    {
      "label": "Organ transplant waitlist mortality (kidney, 5-year)",
      "lifetime_us_adult": 0.1
    },
    {
      "label": "Finding a 6/6 cord blood match",
      "lifetime_us_adult": 0.5
    }
  ],
  "personal_factor_multipliers": [
    {
      "factor": "White / European ancestry",
      "multiplier": 0.6,
      "notes": "Gragert et al. NEJM 2014: 8/8 HLA match probability for White patients is 75%, implying a 25% failure rate vs the 42% population-weighted baseline — approximately 0.60× the average risk. This advantage reflects both the registry's 74% White composition and lower HLA diversity in European-ancestry populations."
    },
    {
      "factor": "Black / African-American ancestry",
      "multiplier": 1.69,
      "notes": "NMDP current data (2025): 71% of Black patients lack a perfectly matched donor worldwide. Relative to the 42% population-weighted failure baseline this is ~1.7×. Root causes are compounding: greater HLA diversity in populations of African descent, AND underrepresentation of Black donors in the registry (≈7% of donors vs ≈13% of US population)."
    },
    {
      "factor": "Multiracial ancestry",
      "multiplier": 1.69,
      "notes": "NMDP current data (2025): 71% of multiracial individuals lack a perfectly matched donor — same rate as Black patients. Individuals of mixed ancestry often fall between population HLA haplotype clusters, making a perfect match statistically rare even in a large registry."
    },
    {
      "factor": "Hispanic / Latino ancestry",
      "multiplier": 1.24,
      "notes": "NMDP current data (2025): 52% of Latino and Hispanic patients lack a perfectly matched donor. Relative to the 42% population-weighted failure rate this is ~1.24×. Gragert et al. (NEJM 2014) reported a 46% 8/8 match probability (54% failure) for Hispanic patients, consistent with the NMDP's updated 52% figure."
    }
  ],
  "short_label": "No marrow match",
  "myth_framing": "underrated",
  "outcome_severity": "serious_harm",
  "exposure_pattern": "acute",
  "outcome_type": "recoverable_injury",
  "valence": "negative",
  "caveats": "The 42% average failure rate applies to optimal 8/8 HLA-matched unrelated donors. Recent advances in haploidentical (half-matched family donor) transplantation and improved mismatched unrelated donor protocols have expanded options significantly. NMDP data from 2024 shows that when 5/8 to 7/8 mismatched donors are considered, virtually all patients have at least one suitable donor available. The clinical question has shifted from \"can we find any donor\" to \"can we find the best donor for optimal outcomes.\"\n",
  "quality_score": {
    "d1": 5,
    "d2": 5,
    "d3": 4,
    "d4": 4,
    "d5": 5,
    "d6": 5,
    "d7": 4,
    "d8": 4,
    "avg": 4.5,
    "scored_by": "claude-code-8d",
    "scored_at": "2026-05-25",
    "methodology_version": "1.2"
  },
  "reviewer": "8d-eval-2026-05-10",
  "last_reviewed": "2026-05-10",
  "reviewed": true,
  "generated_at": "2026-04-18",
  "image": {
    "alt": "Abstract puzzle pieces in muted tones with one piece missing, flat vector illustration representing the challenge of finding a donor match."
  },
  "attribution": "Likelier — https://likelier.app",
  "license": "https://creativecommons.org/licenses/by-sa/4.0/",
  "support": "https://buymeacoffee.com/kgluszczyk?via=likelier&utm_content=api-fear-single",
  "canonical_url": "https://likelier.app/bone-marrow-match-failure"
}