uric acid
Enable an AI agent to recognise uric acid, assess its chemical and physical state in a specified context, and select justified handling, measurement or transformation actions.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise uric acid, assess its chemical and physical state in a specified context, and select justified handling, measurement or transformation actions.
Uric acid is 7,9-dihydro-1H-purine-2,6,8(3H)-trione (C5H4N4O3), the terminal product of purine nucleotide catabolism in humans and other uricase-deficient species; at physiological pH it exists mainly as the urate monoanion, is produced by xanthine oxidoreductase, and is eliminated chiefly by the kidney with a smaller gastrointestinal contribution.
It can be Verify a uric acid assignment against suitable reference evidence and flag unresolved urate or salt identity.; Quantify its occurrence while preserving the measurement basis, matrix and distinction between dissolved and total material.; Assess whether dissolution or precipitation is plausible under specified conditions using applicable evidence.; Select and document sampling, separation or storage conditions that preserve the intended measurand.; Plan a controlled dissolution, crystallisation or chemical conversion with prerequisites, expected outcomes and verification criteria..
Distinguishing features
Check whether structural or reference-matched analytical evidence supports uric acid rather than a name-only assignment or a related purine such as xanthine.
Distinguish the neutral acid from urate species using recorded solution conditions and a justified speciation interpretation; do not treat the labels as chemically interchangeable.
Distinguish uric acid crystals from monosodium urate or other deposits using phase-identification evidence and, where relevant, counterion analysis rather than appearance alone.
Determine whether a reported result identifies uric acid specifically or reports an assay-defined quantity labelled 'uric acid' that includes urate species.
Scope
+ Chemical identity and evidence distinguishing uric acid from related compounds
+ Acid-base speciation and the distinction between uric acid, urate and named urate salts
+ Dissolved, suspended and crystalline occurrences under recorded conditions
+ Amount, concentration, purity and analytical interpretation in a specified matrix
+ Handling, dissolution, precipitation and chemical transformation constraints
- Diagnosis, prognosis and treatment of gout, kidney disease or other patient conditions
- Whole-body purine metabolism and physiological regulation
- Complete composition and behaviour of urine, blood or other host matrices
- Independent substance models for named urate salts, precursors and degradation products
- Laboratory instrument design and general assay operating procedures
Characteristics
- Identity assignment
- confirmed uric acid | provisional uric acid | mixed identity | unresolved Determines whether uric-acid-specific interpretations and actions are justified.
- Identity evidence
- Links to structural identifiers, reference materials, spectra or validated analytical results Makes identification distinguishable from an inherited label.
- Acid-base form
- neutral uric acid | urate species | mixed forms | unresolved Connects the recorded substance to its actual chemical form under the stated conditions.
- Matrix and chemical environment
- Host material or solvent, with linked pH, temperature and relevant ionic composition Provides the context needed to interpret speciation, solubility and assay behaviour.
- Amount or concentration
- mol, g, mol/L or mg/L, with explicit analyte basis and uncertainty Supports comparisons and calculations without conflating free acid, total analytical urate or salt mass.
- Physical occurrence
- dissolved | suspended solid | isolated solid | deposited solid | mixed | unresolved Determines whether sampling, separation or dissolution is needed before an action.
- Solid-phase identity
- Analytically assigned phase or phase mixture, including hydration state where established Prevents visually similar acid and salt deposits from receiving the same interpretation.
- Purity and chemical integrity
- Mass fraction or assay fraction, with named impurities, transformation products and method Determines whether the material remains suitable for its intended analytical or chemical use.
- Saturation assessment
- undersaturated | near equilibrium | supersaturated | undetermined, relative to a specified solid phase Supports decisions about possible precipitation or dissolution without treating concentration alone as decisive.
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.uric-acid
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 16 findings · 28 questions.
Uric acid identity and speciation Establishes what the uric acid label denotes and how the assigned chemical form depends on context.
The agent must distinguish the substance from related purines, urate species and named salts before interpreting its state.
Molecular identity
Connects the substance assignment to evidence that can discriminate related chemical identities.
Uric acid assignment
Records whether the assigned identity is analytically established, inherited from a label or still provisional.
- What structural identifier and reference evidence define the material as uric acid? definition
- What evidence distinguishes it from xanthine, other related purines or an unresolved mixture? measurement
Acid-urate boundary
Separates chemical species, salt identities and analytical naming conventions.
Form under recorded conditions
Records the basis for assigning neutral acid, urate species or a named salt without inferring identity from terminology alone.
- Does 'uric acid' here mean the neutral molecule, an analytical total or a material containing urate species? definition
- Which measured conditions and applicable equilibrium data support the proposed acid-base speciation? measurement
- Does evidence identify a named urate salt that needs a linked substance model? boundary
Uric acid phase and solubility Describes where uric acid occurs physically and what supports an assessment of phase change.
Dissolved analyte, suspended crystals and deposits require different sampling and handling decisions.
Dissolved and solid occurrence
Distinguishes physical fractions and establishes the identity of any solid material.
Phase-resolved occurrence
Records which fractions contain the assigned substance and whether solid-phase identification is sufficient.
- Is the assigned uric acid dissolved, suspended, deposited or distributed across these fractions? measurement
- What phase-identification evidence distinguishes any solid from urate salts or unrelated crystals? measurement
Saturation and phase change
Relates possible dissolution or precipitation to the actual chemical environment and observation period.
Phase-change assessment
Records an evidence-based saturation assessment separately from observed precipitation or dissolution.
- Which solubility or equilibrium evidence applies to the identified solid phase at the recorded pH, temperature and matrix composition? provenance
- What observations establish whether precipitation or dissolution occurred over the relevant time interval? measurement
- What additional evidence is needed before changing conditions to dissolve or recover the material? action
Uric acid quantity and assay meaning Makes uric acid measurements interpretable across matrices, methods and reporting conventions.
A numerical result cannot guide action unless the agent knows what was measured and which material fraction it represents.
Measurand and reporting basis
Defines the chemical and physical scope of each reported quantity.
Interpretable uric acid result
Preserves units, analyte basis and fraction boundaries when recording or converting a result.
- Does the result represent dissolved material, total recoverable material or another explicitly defined fraction? definition
- Is the quantity expressed as uric acid equivalents, a specified urate species or a named salt, and what basis supports any conversion? measurement
Assay and sampling validity
Records whether the method and sample history support the intended interpretation.
Result fitness
Connects assay specificity, matrix effects and sample handling to confidence in the reported uric acid quantity.
- Which method, calibration evidence and matrix-specific interference checks support the result? provenance
- Could filtration, settling, precipitation, dissolution or chemical conversion during handling have changed the measured fraction? measurement
- What confirmation is required before using this result for the proposed material decision? action
Uric acid integrity and interventions Tracks whether the substance remains fit for use and what evidence justifies interventions.
Actions must distinguish preservation of uric acid from changes to its phase, acid-base form or chemical identity.
Chemical integrity and preservation
Records purity, transformation evidence and conditions justified for preserving the intended material.
Uric acid integrity assessment
Separates chemical loss or conversion from redistribution between dissolved and solid forms.
- What evidence shows whether a change in measured uric acid reflects chemical conversion, phase redistribution or analytical interference? measurement
- Which storage and handling conditions are supported for preserving this uric acid material or sample over the required interval? action
Controlled uric acid interventions
Defines proposed operations by their intended chemical outcome and observable completion criteria.
Intervention preconditions and outcome
Records the evidence needed to authorise and verify an operation on the substance without importing clinical treatment decisions.
- Is the intended outcome dissolution, crystallisation, acid-base conversion or conversion into another compound? action
- What material-specific compatibility evidence, procedure and measurements establish that the operation is appropriate and achieved its intended outcome? action
- Does the proposed decision concern this material, or must it be handed to a patient, process or host-matrix model? boundary
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- serum or plasma urate (the routine clinical-chemistry measurand)
- urinary uric acid (spot or 24-hour excretion used in stone-risk and overproduction work-ups)
- monosodium urate monohydrate (the crystal of gout and tophi)
- anhydrous uric acid (a common uric-acid urolith mineral)
- uric acid dihydrate (a distinct uric-acid urolith mineral)
- ammonium acid urate (a related stone salt, not the free acid)
- tissue tophus urate (macroscopic deposits in chronic gout)
- endogenous overproduction versus renal underexcretion hyperuricemia (the two clinical source phenotypes)
- Which of these kinds and varieties hold for the sense of uric acid this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q105522 - Item for the chemical substance uric acid.
- CAS Registry Number - 69-93-2 - Parent free acid, not a specific salt hydrate.
- PubChem CID - 1175 - NCBI compound record for uric acid.
- ChEBI - CHEBI:17775 - ChEBI classifies this as the keto tautomer of the purine triol.
- KEGG Compound - C00366 - Metabolic-map identifier in purine degradation.
- UNII - 268B43CLF9 - FDA Substance Registration System identifier.
- InChIKey - LEHOTFFKMJEONL-UHFFFAOYSA-N - Standard hashed structure key for the parent molecule.
- EC Inventory (EINECS) - 200-720-7 - European chemical inventory number.
- MeSH - D014527 - NLM heading Uric Acid.
- Which of these identifiers and schemes hold for the sense of uric acid this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- 2015 ACR/EULAR gout classification criteria - American College of Rheumatology and European Alliance of Associations for Rheumatology (then EULAR)
- EAU Guidelines on Urolithiasis - European Association of Urology
- AUA guideline on the medical management of kidney stones - American Urological Association
- Guideline for the management of hyperuricemia and gout - Japanese Society of Gout and Uric & Nucleic Acids (defines hyperuricemia as serum urate ≥7.0 mg/dL in both sexes)
- FDA-cleared in-vitro diagnostic uricase assays for serum/plasma/urine uric acid - U.S. Food and Drug Administration
- ICD-10 M10 (gout) and E79.0 (hyperuricemia without inflammatory arthritis or tophaceous disease) - World Health Organization
- Cairo-Bishop laboratory criteria for tumour lysis syndrome, which include a uric-acid threshold - oncology consensus criteria used in practice
- Which of these standards and regulation hold for the sense of uric acid this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Measured in blood as a gout, metabolic-syndrome, preeclampsia, and tumour-lysis analyte.
- Identified as needle-shaped negatively birefringent crystals in synovial fluid to diagnose gout.
- Recovered as radiolucent kidney or bladder stones and typed by infrared spectroscopy as anhydrous uric acid, uric acid dihydrate, or ammonium acid urate.
- Followed in 24-hour urine during metabolic stone evaluation and after urate-lowering or alkalinising therapy.
- Encountered as white paste-like droppings in birds and terrestrial reptiles (uricotelic excretion).
- Used in the laboratory as the substrate of uricase-based assays and as a calibrator/control in clinical chemistry.
- Which of these real-world use hold for the sense of uric acid this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- serum urate, adult men (typical reference interval) - 3.5-7.2 - mg/dL
- serum urate, adult women (typical reference interval) - 2.6-6.0 - mg/dL
- serum urate, SI (adult men, typical) - 210-430 - µmol/L
- aqueous solubility of urate in plasma at 37 °C, pH 7.4 - ~6.8 - mg/dL
- 24-hour urinary uric acid on a mixed diet - 250-750 - mg/day
- fractional excretion of uric acid - 7-12 - %
- first acid dissociation constant (N-3) - ~5.75 - pKa
- molar mass - 168.11 - g/mol
- Which of these typical measurements hold for the sense of uric acid this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Acute gouty arthritis from precipitation of monosodium urate in joints and bursae.
- Chronic tophaceous gout with bone and soft-tissue destruction.
- Uric-acid nephrolithiasis, favoured by persistently acidic urine.
- Acute urate nephropathy in tumour lysis, with intratubular precipitation.
- Xanthine stone risk when xanthine oxidase is blocked in overproducers (iatrogenic neighbour of urate lowering).
- Renal hypouricemia with exercise-induced acute kidney injury in URAT1/GLUT9 loss-of-function.
- Positive or negative interference in older colorimetric uric-acid assays (ascorbate, haemolysis, some drugs); uricase methods are more specific but not immune.
- Supersaturation and precipitation in stored acidic urine specimens.
- Which of these failure modes and hazards hold for the sense of uric acid this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- US laboratories usually report mg/dL; much of Europe, the UK, and Australia report µmol/L (multiply mg/dL by 59.48).
- Clinical chemistry often names the measurand urate; US lab menus and patients still say uric acid.
- Japan commonly defines hyperuricemia as ≥7.0 mg/dL in both sexes; many Western gout guidelines treat below 6.0 mg/dL (or 5.0 with tophi) as a therapeutic target rather than a diagnostic cut-off.
- Gout and mean serum urate are markedly higher in some Pacific, Māori, and Taiwanese populations than in continental European reference groups.
- Dietary drivers differ: fructose-sweetened beverages and beer in high-income settings versus organ-meat and seafood patterns elsewhere.
- Which of these regional variation hold for the sense of uric acid this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- calcium pyrophosphate dihydrate (pseudogout) - Compensated polarized-light microscopy: MSU is needle-shaped and strongly negatively birefringent; CPPD is rhomboid or rod-like and weakly positively birefringent.
- calcium oxalate uroliths - Plain film and CT: oxalate stones are radiopaque and usually higher Hounsfield units; uric-acid stones are radiolucent on plain radiograph and typically <500 HU, confirmed by infrared spectroscopy or dual-energy CT.
- xanthine - Purine panel by HPLC or LC-MS; xanthine accumulates when xanthine oxidase is deficient or inhibited, while urate is low.
- hypoxanthine - Same purine chromatogram: hypoxanthine is the xanthine-oxidase substrate two steps upstream of urate.
- allantoin - Further oxidation product of urate via uricase, which humans lack; LC-MS of allantoin versus uricase-based urate assay separates them.
- urea - Different nitrogenous waste: urease methods measure urea/BUN; uricase methods measure urate; they do not cross-identify.
- ammonium acid urate stone - Stone infrared spectroscopy or XRD: a distinct ammonium salt, often with inflammatory bowel disease or laxative abuse and not equivalent to anhydrous uric acid.
- cholesterol crystals in synovial fluid - Polarized microscopy: large stacked plates or notched rhomboids, not the fine negatively birefringent needles of MSU.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of uric acid this model covers, and on what evidence? provenance
Sources
- PubChem Compound Summary for CID 1175, Uric Acid - National Center for Biotechnology Information - Chemical identity, formula C5H4N4O3, CAS 69-93-2, InChIKey, and linked registry identifiers.
- ChEBI: uric acid (CHEBI:17775) - EMBL-EBI - Ontology identity as the purine-2,6,8-trione, tautomer/salt relations, and cross-references to KEGG and other chemical databases.
- 2015 Gout classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative - Neogi et al., Annals of the Rheumatic Diseases (BMJ) and Arthritis & Rheumatology (Wiley), 2015 - How monosodium urate is distinguished in practice (synovial-fluid microscopy, dual-energy CT, tophi) and the clinical threshold around serum urate.
- EAU Guidelines on Urolithiasis - European Association of Urology - Uric-acid and ammonium-acid-urate stone types, acidic-urine association, and metabolic evaluation including urinary uric acid.
- Regulation of uric acid metabolism and excretion - Maiuolo, Oppedisano, Gratteri, Muscoli, Mollace, International Journal of Cardiology, 2016 - Purine-catabolism pathway, xanthine oxidoreductase as the last human step, renal handling, and the evolutionary absence of uricase in humans.
- Clinical practice. Gout - Terkeltaub, New England Journal of Medicine, Massachusetts Medical Society - Clinical encounter of urate as gout, the plasma saturation point near 6.8 mg/dL, and distinction of MSU disease from other crystal arthropathies.
What the second pass must settle
- Which authoritative identity references and analytical criteria should be adopted for distinguishing uric acid from related purines and named urate salts?
- Which acid-base and solubility datasets are reliable across the intended ranges of temperature, pH and ionic composition, and where do they cease to apply?
- Which uric acid solid phases and hydration states require explicit representation for the intended tasks, and what methods reliably distinguish them?
- How do the intended assays define and report 'uric acid', and which matrix effects and sample-handling changes materially alter their results?
- Which storage, handling and intervention conditions have been validated for the intended material grades, matrices and durations?