12-phase flow (12)

1. 1FRAME
   Adult chronic seronegative spondyloarthropathy across six domains — peripheral arthritis (asymmetric oligo / RA-like poly / DIP-predominant / arthritis mutilans), axial disease, enthesitis, dactylitis, skin psoriasis, nail disease — usually arising on a pre-existing psoriasis substrate (CASPAR; GRAPPA 2021; EULAR 2023)
   inputs: psoriasis_history_and_severity
   advance: scope confirmed (PsA spectrum vs another spondyloarthropathy)
2. 2ENTRY
   Recognise inflammatory arthritis / dactylitis / enthesitis / inflammatory back pain in a psoriasis (esp. nail) patient; screen all psoriasis patients for PsA at dermatology and primary-care visits (ACR/NPF 2021)
   inputs: affected_joint_pattern
   actions: workup.polyarthritis
   advance: entry trigger present and inflammatory (vs mechanical) pattern established
3. 3CONTEXT
   Capture domain map (which of the six domains active + dominant), psoriasis severity/location (scalp, nail, inverse, palmoplantar), IBD/uveitis associations, cardiometabolic comorbidity (obesity, MetS, NAFLD, ASCVD, depression), current systemic psoriasis therapy and steroid exposure (CASPAR; GRAPPA 2021; EULAR 2023)
   inputs: psoriasis_history_and_severity, affected_joint_pattern, inflammatory_back_pain, ibd_history, cardiometabolic_risk, current_systemic_psoriasis_therapy
   advance: domain map + comorbidity + driver profile captured
4. 4RED_FLAGS
   Arthritis mutilans / rapidly destructive polyarthritis, acute anterior uveitis (painful red eye, photophobia), severe/erythrodermic or generalised pustular psoriasis flare, serious infection on biologic/JAKi (sepsis, TB reactivation), axial fragility fracture in long-standing spondylitis (GRAPPA 2021; EULAR 2023)
   inputs: affected_joint_pattern, uveitis_history
   actions: calc.news2, calc.qsofa
   advance: red flags screened; emergent ophthalmology / dermatology / ID escalation triggered if present
5. 5INITIAL_WORKUP
   CRP/ESR, CBC, CMP, RF + anti-CCP (expected negative — seronegative), uric acid (gout overlap), HLA-B27 if axial features, plain radiographs of hands/feet/pelvis (erosion + new bone, pencil-in-cup, sacroiliitis); arthrocentesis if a single hot joint to exclude septic/crystal; metabolic panel (lipids, glucose, NAFLD screen) (CASPAR; GRAPPA 2021; EULAR 2023)
   inputs: crp_esr, rf_anti_ccp, plain_radiographs_hands_feet_pelvis, dactylitis_count, enthesitis_sites
   actions: workup.polyarthritis, panel.inflammation, panel.cbc, panel.cmp, panel.metabolic
   advance: seronegativity confirmed, CASPAR satisfied, radiographs + cardiometabolic baseline obtained
6. 6BRANCHING_WORKUP
   Axial features → MRI sacroiliac joints/spine + HLA-B27; mono/oligoarticular hot joint → arthrocentesis (panel.synovial) to exclude septic arthritis / crystal (gout overlap is common in PsA); enthesitis uncertainty → ultrasound/MRI of entheses; pre-biologic latent-TB (IGRA/PPD) + HBV/HCV serology + age-appropriate malignancy screen (GRAPPA 2021; ACR/NPF 2021)
   inputs: inflammatory_back_pain, tb_hbv_screen
   actions: workup.joint_pain, workup.septic_arthritis, panel.synovial
   advance: domain-specific imaging + pre-biologic infection/malignancy screen complete
7. 7DIFFERENTIAL
   Rheumatoid arthritis (RF/anti-CCP positive, symmetric, no DIP/dactylitis/nail/enthesitis/skin), axial spondyloarthritis (no psoriasis/nail, no peripheral PsA domain), osteoarthritis (DIP Heberden nodes, non-inflammatory), gout/CPPD (crystal — can co-exist), reactive arthritis, IBD-associated arthritis (CASPAR; GRAPPA 2021)
   inputs: rf_anti_ccp, nail_disease
   advance: mimics excluded; PsA confirmed (CASPAR sensitivity 91% / specificity 99%)
8. 8RISK_STRATIFICATION
   Per-domain activity: peripheral via cDAPSA / MDA treat-to-target (DAS28-CRP an imperfect surrogate — misses DIP/dactylitis/enthesitis/axial), axial via BASDAI/ASDAS, skin via BSA/PASI. Poor-prognosis markers: polyarticular involvement, structural damage on radiograph, elevated CRP, dactylitis, functional limitation — escalate earlier and harder (GRAPPA 2021; EULAR 2023)
   inputs: crp_esr, affected_joint_pattern, dactylitis_count
   actions: calc.das28_crp
   advance: activity quantified per active domain; poor-prognosis features flagged; treat-to-target goal set (cDAPSA remission/LDA or MDA)
9. 9TREATMENT
   Treat-to-target by DOMINANT domain (GRAPPA 2021; ACR/NPF 2021; EULAR 2023). Mild mono/oligo: NSAID ± intra-articular steroid + EARLY csDMARD if persistent. Oligo/polyarticular peripheral: csDMARD methotrexate first (also treats skin) / leflunomide / sulfasalazine. Inadequate response OR poor prognosis OR axial- or enthesitis-predominant: bDMARD — TNFi, IL-17i (secukinumab/ixekizumab — strong skin), IL-23i (guselkumab/risankizumab — strong skin, NOT axial-predominant), IL-12/23 ustekinumab; or tsDMARD JAKi (boxed MACE/VTE/malignancy/serious-infection caution); or PDE4i apremilast (milder disease/skin, oral, no lab monitoring). Choose by dominant domain + comorbidity: IBD → avoid IL-17i (use anti-TNF mAb / IL-23i / JAKi); recurrent uveitis → anti-TNF mAb; metabolic/CV burden → weight loss + JAKi caution; pregnancy → certolizumab (minimal placental transfer). AVOID systemic corticosteroids (rebound pustular/erythrodermic psoriasis on taper). Screen/treat latent TB + HBV before biologic, update vaccines (no live vaccines on biologic), co-manage with dermatology, aggressive cardiometabolic risk + weight management. Switch within or across class on primary/secondary failure.
   inputs: affected_joint_pattern, inflammatory_back_pain, ibd_history, cardiometabolic_risk, tb_hbv_screen
   advance: domain-matched therapy started + safety screen cleared + treat-to-target schedule set
10. 10DISPOSITION
    Outpatient rheumatology + dermatology co-management is the default. Inpatient/ED only for: acute uveitis (emergent ophthalmology), erythrodermic/generalised pustular psoriasis (dermatology admission), serious biologic-associated infection/TB reactivation, or arthritis mutilans needing surgical evaluation (GRAPPA 2021; EULAR 2023)
    advance: level of care + multidisciplinary referrals set
11. 11MONITORING
    cDAPSA / MDA every 1–3 months until target then every 3–6 months (treat-to-target). MTX: CBC + LFT + creatinine q2–4 wk during titration then q8–12 wk; leflunomide LFT/BP; sulfasalazine CBC/LFT. Lipids on JAKi (and IL-6 if used). Periodic latent-TB reassessment, HBV monitoring on biologic. Annual cardiometabolic review (lipids, A1c, BMI, NAFLD), depression screening, skin/nail and entheseal exam (GRAPPA 2021; EULAR 2023; ACR/NPF 2021)
    inputs: crp_esr, cardiometabolic_risk
    actions: calc.das28_crp, panel.cbc, panel.cmp, panel.metabolic
    advance: treat-to-target met (cDAPSA remission/LDA or MDA) and sustained ≥6 months on stable regimen
12. 12FOLLOWUP
    Long-term DMARD/biologic continuation with periodic taper consideration at sustained remission; lifelong cardiometabolic risk modification (weight, lipids, glucose, smoking), depression management, dermatology co-care, physical therapy for enthesitis/axial mobility, vaccination upkeep, orthopedic referral for arthritis mutilans / fixed deformity (GRAPPA 2021; EULAR 2023)
    advance: long-term multidisciplinary plan + patient education + return precautions complete