Modified CTSI (mCTSI) Modified CT Severity Index for acute pancreatitis

{
  "categories": [
    {
      "outcome_code": "mild",
      "total_points": "0_or_2",
      "display_range": "0_to_2",
      "severity_word": "mild_mCTSI_imaging_band"
    },
    {
      "outcome_code": "moderate",
      "total_points": "4_or_6",
      "display_range": "4_to_6",
      "severity_word": "moderate_mCTSI_imaging_band"
    },
    {
      "outcome_code": "severe",
      "total_points": "8_or_10",
      "display_range": "8_to_10",
      "severity_word": "severe_mCTSI_imaging_band"
    }
  ],
  "applicability": {
    "use_for": "Adults with acute pancreatitis when contrast-enhanced CT has been clinically obtained and is technically adequate to assess enhancement, necrosis and extrapancreatic complications.",
    "classification_unit": "one_acute_pancreatitis_episode_at_one_CECT_timepoint",
    "required_inputs": [
      "CECT_date_and_time_from_symptom_onset",
      "pancreatic_and_peripancreatic_inflammation_state",
      "enhancing_versus_nonenhancing_pancreatic_parenchyma",
      "estimated_necrosis_percentage",
      "presence_of_at_least_one_defined_extrapancreatic_complication"
    ],
    "outside_scope": [
      "unenhanced_CT_necrosis_scoring",
      "MRI_or_ultrasound_numeric_substitution",
      "chronic_pancreatitis",
      "postoperative_pancreatic_change_without_acute_pancreatitis",
      "clinical_organ_failure_severity_assignment",
      "treatment_selection"
    ]
  },
  "component_scoring": {
    "pancreatic_inflammation": [
      {
        "points": 0,
        "finding": "normal_pancreas"
      },
      {
        "points": 2,
        "finding": "intrinsic_pancreatic_abnormality_with_or_without_inflammatory_change_in_peripancreatic_fat"
      },
      {
        "points": 4,
        "finding": "pancreatic_or_peripancreatic_fluid_collection_OR_peripancreatic_fat_necrosis"
      }
    ],
    "pancreatic_necrosis": [
      {
        "points": 0,
        "finding": "none"
      },
      {
        "points": 2,
        "finding": "less_than_or_equal_to_30_percent"
      },
      {
        "points": 4,
        "finding": "greater_than_30_percent"
      }
    ],
    "extrapancreatic_complications": {
      "points_if_none": 0,
      "points_if_one_or_more": 2,
      "noncumulative_rule": "The presence of one or several qualifying complications contributes one 2-point term; do not add 2 points per complication.",
      "qualifying_groups": [
        "pleural_effusion",
        "ascites",
        "vascular_complication",
        "extrapancreatic_parenchymal_complication",
        "gastrointestinal_tract_involvement"
      ]
    }
  },
  "calculation_and_assignment_algorithm": [
    "Score exactly one mutually exclusive pancreatic-inflammation state as 0, 2 or 4.",
    "On adequate CECT, score pancreatic necrosis as none 0, 30 percent or less 2, or more than 30 percent 4; exactly 30 percent remains 2.",
    "Add 2 once if at least one defined extrapancreatic complication is present, regardless of how many groups are present.",
    "Sum the three components. Only 0, 2, 4, 6, 8 and 10 are reachable.",
    "Map totals 0 or 2 to mild, 4 or 6 to moderate, and 8 or 10 to severe."
  ],
  "decisive_boundaries": {
    "impossible_totals": "Totals 1, 3, 5, 7 and 9 cannot be produced by the published component values; reject them as calculation or transcription errors.",
    "exact_30_percent_necrosis": "Thirty percent receives 2 points; only a value greater than 30 percent receives 4.",
    "mild_boundary": "The modified index has mild 0-2, not the original CTSI 0-3 band.",
    "severe_boundary": "The modified index has severe 8-10, not the original CTSI 7-10 band."
  },
  "CT_timing_and_adequacy": {
    "initial_diagnosis_rule": "Acute pancreatitis is ordinarily diagnosed clinically and biochemically; CT is reserved when diagnosis is uncertain or the patient fails to improve, not ordered merely to obtain mCTSI.",
    "early_underestimation": "Early imaging can underestimate evolving necrosis. Record time from symptom onset and avoid treating a low early score as final reassurance.",
    "current_ACG_context": "The 2024 ACG guideline reserves CT for uncertain diagnosis or failure to improve after 48 to 72 hours.",
    "revised_Atlanta_context": "When characterization of necrosis is needed, the Revised Atlanta consensus notes that CECT after about 5 to 7 days is more reliable than very early CT.",
    "contrast_gate": "If IV contrast is absent, contraindicated or technically nondiagnostic for enhancement, do not assign a definitive necrosis component or total mCTSI."
  },
  "risk_interpretation": {
    "relative_burden": "Higher totals represent greater CT inflammatory, necrotic and extrapancreatic-complication burden and are associated at cohort level with worse clinical outcomes.",
    "no_personal_probability": "A band supplies no calibrated individual probability of persistent organ failure, ICU admission, intervention, length of stay or death.",
    "discrimination_boundary": "Published AUCs summarize discrimination in pooled cohorts and must not be reported as a patient's probability or as a category-specific event rate.",
    "act_on_findings": "Actual organ failure, infection, hemorrhage, thrombosis, obstruction and other actionable complications remain separate findings and can be urgent at any total."
  },
  "management_boundary": {
    "no_band_order": "No mCTSI band alone determines ward versus ICU care, antibiotics, nutrition, ERCP, drainage, necrosectomy, surgery, anticoagulation or discharge.",
    "current_care_inputs": [
      "hemodynamics_and_organ_failure",
      "infection_status",
      "symptoms_and_trajectory",
      "collection_type_and_maturity",
      "hemorrhage_or_vessel_involvement",
      "biliary_obstruction_or_cholangitis",
      "multidisciplinary_local_protocol"
    ],
    "report_actionable_details": "Communicate individual complications directly and urgently when warranted rather than hiding them behind the aggregate band."
  },
  "system_collision_boundary": {
    "original_Balthazar_CTSI": "The original CTSI uses Balthazar grade A-E plus four necrosis brackets and bands 0-3, 4-6 and 7-10. Do not reuse those cutoffs for mCTSI.",
    "Revised_Atlanta": "Revised Atlanta clinical severity is based on organ failure duration and local or systemic complications. Shared words mild, moderate or severe do not create a numeric crosswalk.",
    "APACHE_BISAP_and_Ranson": "These are separate clinical or laboratory prognostic tools and cannot be reconstructed from CT findings."
  },
  "agent_output_contract": [
    "Return CT contrast adequacy, examination date, estimated time from symptom onset and comparison date.",
    "Return each component finding, its points, necrosis percentage and the noncumulative extrapancreatic-complication list before the total.",
    "Return the arithmetic sum, one of the six reachable totals and the named mCTSI band.",
    "Keep Revised Atlanta clinical severity, morphology and collection terminology in separate fields.",
    "Return every actionable complication explicitly and do not derive treatment or a patient probability from the band."
  ],
  "missing_input_behavior": [
    "If IV contrast enhancement is unavailable or nondiagnostic, return mCTSI_not_calculable rather than assuming zero necrosis.",
    "If the necrosis estimate straddles 30 percent, return the bounded uncertainty and both possible totals or request expert review rather than selecting the more reassuring value.",
    "If CT was obtained very early, label possible underestimation and do not extrapolate a final course.",
    "If a reported total is odd, recompute the components and reject the odd number.",
    "If only a band is supplied, do not infer its component findings, exact total, Revised Atlanta grade or treatment."
  ],
  "supporting_sources": [
    {
      "role": "original_modified_index",
      "citation": "Mortele et al. AJR. 2004;183:1261-1265",
      "doi": "10.2214/ajr.183.5.1831261"
    },
    {
      "role": "revised_Atlanta_collision_and_timing",
      "citation": "Banks et al. Gut. 2013;62:102-111",
      "doi": "10.1136/gutjnl-2012-302779"
    },
    {
      "role": "current_CT_and_management_context",
      "citation": "Tenner et al. Am J Gastroenterol. 2024;119:419-437",
      "doi": "10.14309/ajg.0000000000002645"
    },
    {
      "role": "pooled_discrimination_boundary",
      "citation": "Mikó et al. Front Physiol. 2019;10:1002",
      "doi": "10.3389/fphys.2019.01002",
      "pmcid": "PMC6718714"
    }
  ],
  "source_locator": "Mortele et al. AJR 2004, DOI 10.2214/ajr.183.5.1831261, modified-index table and severity groups; Mikó et al. 2019, PMC6718714, Table 1B and meta-analysis results; Banks et al. Revised Atlanta consensus, DOI 10.1136/gutjnl-2012-302779, morphology, severity and CECT timing; Tenner et al. ACG 2024 guideline, DOI 10.14309/ajg.0000000000002645, imaging and treatment context."
}