12-phase flow (12)

1. 1FRAME
   Adult acute gout FLARE / acute monoarthritis at the primary-care or ED front door — triage, exclude the septic cannot-miss, abort, and ROUTE chronic urate management out (this is not the ULT engine) (ACR 2020 FitzGerald PMID 32391934; ACP 2017 Qaseem PMID 27802508)
   inputs: joint_involved_and_onset_hours
   advance: Acute-monoarthritis scope confirmed; chronic ULT recognised as out-of-scope (routed)
2. 2ENTRY
   Hot swollen painful joint (classically podagra/1st MTP), with or without fever; recurrent self-limited episodes; or known gout on ULT now flaring (ACR 2020 FitzGerald PMID 32391934)
   inputs: joint_involved_and_onset_hours
   advance: Engine entered via a recognised acute-monoarthritis trigger
3. 3CONTEXT
   Prior identical podagra episodes (raises gout prior), current ULT (CONTINUE through flare — never stop; do NOT start here), alcohol/diuretic/transplant drivers, comorbidity inventory for abort-drug gating (ACR 2020 FitzGerald PMID 32391934; ACP 2017 PMID 27802508)
   inputs: prior_identical_flares, current_ult
   advance: Flare history + ULT status + driver profile captured
4. 4RED_FLAGS
   SEPTIC ARTHRITIS cannot-miss — gout and septic arthritis CAN co-exist; crystal-positive does NOT exclude infection. Pre-test ≈10% in ED acute swollen-joint cohorts (653/6242); fever sensitivity ONLY 57% so absence does NOT exclude; risk factors (age, DM, RA, prosthetic/operated joint, skin infection, HIV, IVDU, immunosuppression) raise probability. T_aspirate = any acute monoarthritis → STAT arthrocentesis BEFORE anti-inflammatory commitment (Margaretten JAMA 2007 PMID 17405973; ACR 2020 PMID 32391934)
   inputs: temperature, septic_arthritis_risk_factors
   actions: workup.acute_monoarthritis, panel.synovial
   advance: Septic arthritis actively screened; arthrocentesis sent (or escalation fired if purulent / high prior)
5. 5INITIAL_WORKUP
   Arthrocentesis-first: synovial cell count + differential + Gram + crystal exam (negatively birefringent needle MSU = gout; positively birefringent rhomboid = CPPD). Synovial WBC bands LR: <25k LR 0.32 (0.23-0.43), ≥25k LR 2.9 (2.5-3.4), >50k LR 7.7 (5.7-11.0), >100k LR 28.0 (12.0-66.0); PMN ≥90% LR 3.4 (2.8-4.2), <90% LR 0.34 (0.25-0.47). Add CBC/CRP/ESR (raised in BOTH — do not discriminate) and creatinine for abort-drug eGFR. SUA frequently normal in flare (LR ≈ 1 — does not rule in/out) (Margaretten JAMA 2007 PMID 17405973; ACR 2020 PMID 32391934)
   inputs: synovial_fluid_analysis, serum_uric_acid, inflammatory_markers_crp_esr, creatinine
   actions: panel.synovial, panel.cbc, panel.inflammation, panel.renal
   advance: Synovial analysis resulted (cell count/PMN/Gram/crystal) and renal function known
6. 6BRANCHING_WORKUP
   Gram-positive / purulent / WBC >50k band with high prior → empiric anti-staph + drainage + route septic engine. Negatively birefringent MSU + septic adequately excluded → confirmed gout flare. Positively birefringent rhomboid + chondrocalcinosis → CPPD sibling. Immunosuppressed/prosthetic host → down-weight a "low" synovial-WBC LR (conditional dependence) (Margaretten JAMA 2007 PMID 17405973; ACR 2020 PMID 32391934)
   inputs: synovial_fluid_analysis
   actions: workup.joint_pain
   advance: Crystal identity + septic-arthritis probability resolved (or escalated)
7. 7DIFFERENTIAL
   Gout (MSU) vs SEPTIC ARTHRITIS (co-existence — NOT mutually exclusive) vs CPPD/pseudogout (look-alike) vs trauma/haemarthrosis vs cellulitis overlying a joint vs mono-onset psoriatic/reactive arthritis. Pivot = synovial WBC/PMN/Gram/crystal + clinical prior; crystal-positivity is conditionally INDEPENDENT of infection (Margaretten JAMA 2007 PMID 17405973; EULAR 2016 Richette PMID 27457514)
   inputs: synovial_fluid_analysis
   advance: Septic arthritis excluded/escalated and crystal arthropathy assigned
8. 8RISK_STRATIFICATION
   Septic probability tier from synovial WBC band + PMN + Gram + host risk factors + conditional-dependence down-weighting (immunosuppressed/prosthetic/partially-treated). T_treat_empiric = purulence/Gram-positive/high-count+high-prior/sepsis → empiric anti-staph + drainage + route NOW (treatment benefit > test-delay cost) (Margaretten JAMA 2007 PMID 17405973)
   inputs: synovial_fluid_analysis, septic_arthritis_risk_factors
   advance: Septic vs crystal probability tier set; empiric-treat threshold evaluated
9. 9TREATMENT
   ABORT the flare within 24 h, comorbidity-gated (ACR 2020 equal first-line: colchicine/NSAID/steroid). Low-dose colchicine 1.2 mg → 0.6 mg 1 h later then 0.6 mg q12h-daily (AGREE: 37.8% vs 15.5% placebo responders at 24 h, P=0.005; low-dose AE = placebo OR 1.5 [0.7-3.2]); NSAID (naproxen 500 BID / indomethacin 50 TID) if no CKD/CVD/PUD; oral prednisone 40 mg/d ×5 d or IA/IM steroid if NSAID/colchicine contraindicated; anakinra 100 mg SC daily ×3-5 d IL-1 RESCUE when all three first-line classes contraindicated/refractory (EULAR 2016). eGFR (race-neutral CKD-EPI 2021) gates colchicine/NSAID. CONTINUE existing ULT; do NOT start/stop ULT here — route ULT decision to msk.gout-chronic.core.v1 (ACR 2020 PMID 32391934; AGREE PMID 20131255; EULAR 2016 PMID 27457514; ACP 2017 PMID 27802508)
   inputs: ckd_stage_egfr, cvd_hf_uncontrolled_htn, pud_gi_bleed_anticoagulation, cyp3a4_or_pgp_inhibitors, current_ult, creatinine
   actions: calc.ckd_epi_2021
   advance: Comorbidity-gated abort regimen started (or septic pathway escalated); ULT continued if pre-existing
10. 10DISPOSITION
    Discharge home with abort regimen + chronic-engine follow-up for the ULT shared decision (do NOT start ULT in the ED/clinic for a first/infrequent attack — ACP 2017). ADMIT / escalate if septic arthritis suspected, refractory flare, unable to tolerate oral therapy, or comorbid decompensation (ACR 2020 PMID 32391934; ACP 2017 PMID 27802508)
    advance: Level of care set; septic escalation vs home-with-follow-up decided
11. 11MONITORING
    Pain/inflammation trajectory 24-48 h (AGREE response window); BMP pre/post NSAID course if renal risk; glucose if steroid + diabetes; CK if colchicine + interacting drug. Failure to improve in 48 h → reassess diagnosis (occult septic / CPPD) (ACR 2020 PMID 32391934; AGREE PMID 20131255)
    inputs: creatinine
    actions: panel.renal
    advance: Flare improving on the abort regimen, or re-triaged for non-response
12. 12FOLLOWUP
    Route to msk.gout-chronic.core.v1 for the longitudinal ULT shared decision (≥2 flares/yr, tophus, CKD≥3, urolithiasis, or already on ULT). Counsel: this acute engine ABORTS and REFERS — it does not manage urate. Return precautions: fever + hot joint, rapid worsening, no improvement in 48 h (ACP 2017 Qaseem PMID 27802508; ACR 2020 PMID 32391934)
    advance: Chronic-engine handoff booked + return precautions given