{"id":"fab4fdb1-71e0-5622-8ceb-d7b5dd817690","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-deficiency-homocysteine-frequency","predicate":"clinical_deficiency_often_elevated_homocysteine","statement":"Total homocysteine was elevated in 95.9% of the B12-deficiency episodes; it was also elevated in 91% of the folate-deficiency episodes.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"dbfc58b6-0c9f-545a-8ace-acedf6a6acca","mechanism_event_label":"This marker is shared by connected nutrient pathways, so it cannot identify B12 deficiency by itself.","subject":{"id":"b6d9b937-895d-5e0a-8cc5-0454a0b7d373","slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"},"object":{"id":"5b635b42-bc0d-5c54-aa94-9cf76cd0ed47","slug":"homocysteine","display_name":"Homocysteine","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"dbfc58b6-0c9f-545a-8ace-acedf6a6acca","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-deficiency-homocysteine-frequency-event","event_type":"observed_intervention","label":"This marker is shared by connected nutrient pathways, so it cannot identify B12 deficiency by itself.","description":"Total homocysteine was elevated in 95.9% of the B12-deficiency episodes; it was also elevated in 91% of the folate-deficiency episodes.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"e176a266-711e-5469-89da-3fb2d3f244ad","slug":"folate","display_name":"Folate (vitamin B9)","entity_type_key":"chemical_species"},"role":"alternative_nutrient_dependency","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"b6d9b937-895d-5e0a-8cc5-0454a0b7d373","slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"5b635b42-bc0d-5c54-aa94-9cf76cd0ed47","slug":"homocysteine","display_name":"Homocysteine","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"availability_state","value_text":"biomarker_context","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null},{"dimension":"cross_nutrient","value_text":"Folate and B12 both participate in homocysteine remethylation.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Selected clear-cut deficiency series: 434 B12 episodes in 406 patients and 123 folate episodes in 119 patients.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Serum MMA and total homocysteine assays; elevation defined above three standard deviations of the reference mean.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Circulating concentration is not a direct MTR activity measurement.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"This marker is shared by connected nutrient pathways, so it cannot identify B12 deficiency by itself.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[b12-savage1994] Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies (1994). https://pubmed.ncbi.nlm.nih.gov/8154512/ DOI: 10.1016/0002-9343(94)90149-x","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Human blood or whole-person endpoints","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"trigger_kind","value_text":"biomarker_context","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null}],"evidence":[{"id":"b59a4899-4e58-55a1-a54c-00edc77a3209","evidence_kind":"source_excerpt","locator":"Lines 1474-1485","start_line":1474,"end_line":1485,"excerpt":"### b12-deficiency-homocysteine-frequency\nTotal homocysteine was elevated in 95.9% of the B12-deficiency episodes; it was also elevated in 91% of the folate-deficiency episodes.\nCondition category: biomarker_context\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: This marker is shared by connected nutrient pathways, so it cannot identify B12 deficiency by itself.\norganism: Homo sapiens\ntissue_or_cell_type: Human blood or whole-person endpoints\nexperimental_model: Selected clear-cut deficiency series: 434 B12 episodes in 406 patients and 123 folate episodes in 119 patients.\nlimitations: Circulating concentration is not a direct MTR activity measurement.\nexposure: Serum MMA and total homocysteine assays; elevation defined above three standard deviations of the reference mean.\ncross_nutrient: Folate and B12 both participate in homocysteine remethylation.\n[b12-savage1994] Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies (1994). https://pubmed.ncbi.nlm.nih.gov/8154512/ DOI: 10.1016/0002-9343(94)90149-x","model_system":"Selected clear-cut deficiency series: 434 B12 episodes in 406 patients and 123 folate episodes in 119 patients.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [b12-savage1994] Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies (1994). https://pubmed.ncbi.nlm.nih.gov/8154512/ DOI: 10.1016/0002-9343(94)90149-x","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"73145023-2982-5848-aff2-8d8875d6b9c5","stable_key":"import-7fc92b9e-9cbf-556e-8719-6b5244625250","title":"Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"ad5b3a51d36e856aa7fdfd1cc23f690b094689bad87d28e1a621a54675a01c92","revision_id":"118bd616-0c13-549f-bfeb-bc439715b89c","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}