Clinical Knowledge

Clinical Reference Knowledge

Regulatory Context

The 21st Century Cures Act (2016) and ONC's Interoperability Final Rule (2020) require US healthcare organizations to expose patient data through standardized FHIR APIs. As of 2024, ~70% of US hospitals support FHIR R4 (source: ONC). CMS ties quality measure reporting to reimbursement through programs like MIPS (Merit-based Incentive Payment System) and the Hospital Value-Based Purchasing Program. Failure to report -- or poor performance -- results in payment adjustments of up to 9%.

HIPAA (Health Insurance Portability and Accountability Act) prohibits transmitting Protected Health Information (PHI) to external services without a BAA (Business Associate Agreement). This is the primary reason clinical AI must run locally: cloud LLM APIs are not BAA-covered by default, and even those that offer BAAs (e.g., Azure OpenAI) face institutional resistance from hospital compliance teams.

Common Lab Reference Ranges

These are general adult reference ranges. Values vary by lab, assay, and patient characteristics. Always defer to the performing laboratory's reference range when available via FHIR referenceRange.

| Lab | Normal Range | Concerning | Unit | Notes |

|-----|-------------|------------|------|-------|

| HbA1c | < 5.7% (non-diabetic), < 7.0% (diabetic target) | > 9.0% = poor control | % | ADA 2024 guidelines; target may be relaxed to < 8.0% for elderly/frail |

| Fasting Glucose | 70-100 | 100-125 = prediabetes, >= 126 = diabetic | mg/dL | Must be fasting; random glucose >= 200 also diagnostic |

| Creatinine | 0.7-1.3 (male), 0.6-1.1 (female) | > 1.5 = impaired renal | mg/dL | Affected by muscle mass; less reliable in elderly |

| eGFR | > 90 (normal), 60-89 (mild decrease) | 30-59 = moderate CKD, 15-29 = severe, < 15 = kidney failure | mL/min/1.73m2 | CKD-EPI 2021 equation (race-neutral) |

| BUN | 7-20 | > 20 with rising creatinine = renal concern | mg/dL | Elevated by dehydration, high protein diet |

| Total Cholesterol | < 200 | 200-239 = borderline, >= 240 = high | mg/dL | |

| LDL | < 100 (general), < 70 (high-risk ASCVD) | > 160 = high | mg/dL | ACC/AHA 2018 |

| HDL | > 40 (male), > 50 (female) | < 40 = cardiovascular risk factor | mg/dL | |

| Triglycerides | < 150 | 150-499 = elevated, >= 500 = severe (pancreatitis risk) | mg/dL | |

| Systolic BP | < 120 (normal), 120-129 (elevated) | 130-139 = Stage 1 HTN, >= 140 = Stage 2 HTN | mmHg | ACC/AHA 2017; CMS165 uses 140/90 threshold |

| Diastolic BP | < 80 | 80-89 = Stage 1 HTN, >= 90 = Stage 2 HTN | mmHg | |

| BNP | < 100 | 100-400 = possible HF, > 400 = likely HF | pg/mL | Age-adjusted: higher cutoffs in elderly; obesity lowers BNP |

| NT-proBNP | < 300 (rule-out) | Age-stratified: >450 (<50y), >900 (50-75y), >1800 (>75y) | pg/mL | More stable than BNP; renal clearance affects levels |

| Potassium | 3.5-5.0 | < 3.5 = hypokalemia, > 5.5 = hyperkalemia (cardiac risk) | mEq/L | Critical for patients on ACEi/ARB/spironolactone |

| Sodium | 136-145 | < 130 = moderate hyponatremia | mEq/L | Common in HF patients |

| ALT | 7-56 | > 3x ULN = significant hepatotoxicity | U/L | Monitor with statin therapy |

| Hemoglobin | 13.5-17.5 (male), 12.0-16.0 (female) | < 12 (male) or < 11 (female) = anemia | g/dL | Common in CKD (erythropoietin deficiency) |

When reporting lab values:

• Always flag values outside the normal range with the severity (mild / moderate / severe)
• Note the date of the observation -- a result from 2 years ago has different clinical significance than one from yesterday
• If the FHIR Observation includes a referenceRange, use that instead of the table above

Condition Codes

SNOMED CT Codes (Primary)

| Code | Condition | ICD-10 Equivalent | Prevalence (US adults) |

|------|-----------|-------------------|----------------------|

| 44054006 | Type 2 Diabetes Mellitus | E11.x | ~11% (37M) |

| 46635009 | Type 1 Diabetes Mellitus | E10.x | ~0.5% (1.6M) |

| 38341003 | Essential Hypertension | I10 | ~47% (116M) |

| 84114007 | Heart Failure | I50.x | ~2.4% (6.7M) |

| 40055000 | Chronic Kidney Disease | N18.x | ~15% (37M) |

| 53741008 | Coronary Artery Disease | I25.x | ~7% (20M) |

| 13645005 | COPD | J44.x | ~6% (16M) |

| 195967001 | Asthma | J45.x | ~8% (25M) |

| 49436004 | Atrial Fibrillation | I48.x | ~2% (6M) |

| 73211009 | Diabetes (unspecified) | E11.9 | Used in older records |

ICD-10-CM to SNOMED Crosswalk

When FHIR Condition resources use ICD-10 coding (system http://hl7.org/fhir/sid/icd-10-cm), map as follows:

• E11.* → Type 2 Diabetes (SNOMED 44054006)
• E10.* → Type 1 Diabetes (SNOMED 46635009)
• I10 → Essential Hypertension (SNOMED 38341003)
• I50.* → Heart Failure (SNOMED 84114007)
• N18.* → Chronic Kidney Disease (SNOMED 40055000)

Note: A Condition resource may have both SNOMED and ICD-10 codes in the coding array. Always check all entries, not just coding[0].

CMS Quality Measures

CMS122v12 -- Diabetes: Hemoglobin A1c (HbA1c) Poor Control (> 9%)

| Component | Definition |

|-----------|-----------|

| Denominator | Patients 18-75 with diabetes (Type 1 or Type 2) and at least 2 encounters during the measurement period |

| Numerator | Patients with most recent HbA1c > 9.0%, OR no HbA1c recorded during the measurement period |

| Exclusions | Hospice care, palliative care, advanced illness with frailty (2+ encounters for advanced illness AND frailty diagnosis), dementia medications (donepezil, rivastigmine, memantine, galantamine) |

| Performance rate | Lower is better (inverse measure) |

| Payment impact | Part of MIPS quality reporting; affects Medicare reimbursement |

CMS165v12 -- Controlling High Blood Pressure

| Component | Definition |

|-----------|-----------|

| Denominator | Patients 18-85 with essential hypertension diagnosed before or during the measurement period |

| Numerator | Patients with most recent BP < 140/90 mmHg |

| Exclusions | Hospice, palliative care, ESRD, kidney transplant, advanced illness with frailty, pregnancy |

| Performance rate | Higher is better |

| Note | BP must be measured during an outpatient encounter; home BP readings are not counted in the standard measure |

CMS135v12 -- Heart Failure: ACEi/ARB/ARNI Therapy for LVEF < 40%

| Component | Definition |

|-----------|-----------|

| Denominator | Patients 18+ with heart failure AND documented LVEF < 40% (HFrEF) |

| Numerator | Patients prescribed ACE inhibitor, ARB, or ARNI (sacubitril/valsartan) |

| Exclusions | Hospice, allergy/intolerance to all three classes, bilateral renal artery stenosis, pregnancy, hyperkalemia > 5.5 |

| Note | LVEF data often in DiagnosticReport or CarePlan, not always queryable via Condition alone |

CMS134v12 -- Diabetes: Medical Attention for Nephropathy

| Component | Definition |

|-----------|-----------|

| Denominator | Patients 18-75 with diabetes |

| Numerator | Patients with nephropathy screening (urine albumin test) OR evidence of nephropathy treatment (ACEi/ARB) OR nephropathy diagnosis |

| Exclusions | Hospice, palliative care, advanced illness with frailty |

Drug Classifications

When checking medication coverage, recognize these drug class groupings. Matching should be case-insensitive partial string matching on the medication name from FHIR medicationCodeableConcept.text or .coding[].display.

Diabetes Medications

| Class | Drugs | Notes |

|-------|-------|-------|

| Biguanide | metformin | First-line therapy |

| Sulfonylureas | glipizide, glyburide, glimepiride | Hypoglycemia risk |

| Insulin | insulin lispro, insulin glargine, insulin aspart, insulin detemir, insulin degludec, NPH insulin | Match any string containing "insulin" |

| GLP-1 Receptor Agonists | liraglutide (Victoza), semaglutide (Ozempic/Wegovy/Rybelsus), dulaglutide (Trulicity), exenatide (Byetta/Bydureon), tirzepatide (Mounjaro) | Weight loss benefit; cardiovascular benefit |

| SGLT2 Inhibitors | empagliflozin (Jardiance), dapagliflozin (Farxiga), canagliflozin (Invokana), ertugliflozin (Steglatro) | Cardiovascular + renal benefit; monitor for DKA |

| DPP-4 Inhibitors | sitagliptin (Januvia), saxagliptin, linagliptin, alogliptin | Weight-neutral |

| Thiazolidinediones | pioglitazone, rosiglitazone | HF risk; edema |

Antihypertensives

| Class | Drugs | Notes |

|-------|-------|-------|

| ACE Inhibitors | lisinopril, enalapril, ramipril, benazepril, fosinopril, quinapril | Cough side effect; monitor K+ and creatinine |

| ARBs | losartan, valsartan, irbesartan, olmesartan, telmisartan, candesartan, azilsartan | Alternative if ACEi cough |

| ARNIs | sacubitril/valsartan (Entresto) | HFrEF guideline-directed; do NOT combine with ACEi |

| CCBs | amlodipine, nifedipine, diltiazem, verapamil | Diltiazem/verapamil contraindicated in HFrEF |

| Beta-Blockers | metoprolol (tartrate or succinate), atenolol, carvedilol, bisoprolol, propranolol, nebivolol | Only carvedilol, metoprolol succinate, bisoprolol for HF |

| Thiazide Diuretics | hydrochlorothiazide (HCTZ), chlorthalidone, indapamide | First-line for HTN |

| Loop Diuretics | furosemide, bumetanide, torsemide | Volume management in HF, not primary HTN therapy |

| Aldosterone Antagonists | spironolactone, eplerenone | HF benefit; monitor K+ |

Statins (HMG-CoA Reductase Inhibitors)

| Intensity | Drugs |

|-----------|-------|

| High | atorvastatin 40-80mg, rosuvastatin 20-40mg |

| Moderate | atorvastatin 10-20mg, rosuvastatin 5-10mg, simvastatin 20-40mg, pravastatin 40-80mg |

| Low | simvastatin 10mg, pravastatin 10-20mg, lovastatin 20mg |

Heart Failure Medications (Guideline-Directed Medical Therapy)

The four pillars of HFrEF therapy (ACC/AHA 2022):

• ACEi/ARB/ARNI -- sacubitril/valsartan preferred over ACEi/ARB
• Beta-Blocker -- carvedilol, metoprolol succinate, or bisoprolol only
• Aldosterone Antagonist -- spironolactone or eplerenone (if eGFR > 30, K+ < 5.0)
• SGLT2 Inhibitor -- dapagliflozin or empagliflozin (regardless of diabetes status)

Matching Strategy

medication_name = fhir_med_text.lower()

is_on_insulin = "insulin" in medication_name
is_on_glp1 = any(drug in medication_name for drug in
    ["liraglutide", "semaglutide", "dulaglutide", "exenatide", "tirzepatide",
     "victoza", "ozempic", "trulicity", "byetta", "mounjaro", "rybelsus"])
is_on_sglt2 = any(drug in medication_name for drug in
    ["empagliflozin", "dapagliflozin", "canagliflozin", "ertugliflozin",
     "jardiance", "farxiga", "invokana", "steglatro"])
is_on_acei = any(drug in medication_name for drug in
    ["lisinopril", "enalapril", "ramipril", "benazepril", "fosinopril", "quinapril"])
is_on_arb = any(drug in medication_name for drug in
    ["losartan", "valsartan", "irbesartan", "olmesartan", "telmisartan",
     "candesartan", "azilsartan"])
is_on_betablocker = any(drug in medication_name for drug in
    ["metoprolol", "atenolol", "carvedilol", "bisoprolol", "propranolol", "nebivolol"])
is_on_statin = any(drug in medication_name for drug in
    ["atorvastatin", "rosuvastatin", "simvastatin", "pravastatin", "lovastatin"])

Clinical Comorbidity Patterns

Common co-occurring conditions to watch for during analysis:

• Cardiorenal-metabolic overlap: Diabetes + Hypertension + CKD occur together in ~30% of diabetic patients
• Heart failure + CKD: eGFR < 30 limits medication options (spironolactone, SGLT2i dose adjustment)
• Diabetes + CAD: Statin therapy should be high-intensity; GLP-1/SGLT2i have cardiovascular benefit
• Atrial fibrillation + Heart failure: Common pairing; rate control with beta-blocker preferred

Guardrails

• These reference ranges are general guidelines based on published clinical guidelines (ADA, ACC/AHA, KDIGO), not diagnostic criteria
• Never state that a patient "has" a condition based on a lab value alone
• Always include the disclaimer: "This is for informational and research purposes, not clinical decision-making"
• When flagging care gaps, use language like "may warrant review" not "requires treatment"
• Acknowledge that CMS measure logic here is simplified -- production implementations use the full eCQM (electronic Clinical Quality Measure) specifications from CMS
• Lab reference ranges should defer to the performing laboratory's range when available