Langcare Langcare MCP Fhir Lab Result Interpreter

Lab Result Interpreter

Overview

Pull laboratory Observation resources for a patient. Organize by panel type (CBC, BMP, CMP, liver, lipids, thyroid, coagulation, urinalysis). Flag abnormal values using the interpretation field and referenceRange. Calculate delta checks against prior results to detect clinically significant changes. Identify critical values requiring immediate action. Correlate abnormal patterns with differential diagnoses. Present results in structured clinical format with trend analysis.

FHIR Resources Used

Instructions

Step 1: Retrieve Patient Demographics

Tool: fhir_read
resourceType: "Patient"
id: "[patient-id]"

Extract birthDate (calculate age) and gender. These determine reference range selection -- many analytes have age- and sex-specific ranges.

Step 2: Pull Recent Laboratory Observations

Tool: fhir_search
resourceType: "Observation"
queryParams: "patient=[patient-id]&category=laboratory&date=ge[target-date]&_sort=-date&_count=200"

If user requests a specific panel, narrow with LOINC codes:

• CBC panel: code=58410-2
• BMP: code=51990-0
• CMP: code=24323-8
• Liver panel: code=24325-3
• Lipid panel: code=57698-3
• Thyroid panel: code=3016-3,3026-2,3024-7

Default date range: ge[30-days-ago] unless user specifies otherwise.

Step 3: Organize Results by Panel Category

Group Observations by code.coding LOINC into:

• CBC: WBC (26464-8), RBC (789-8), Hemoglobin (718-7), Hematocrit (4544-3), MCV (787-2), MCH (785-6), MCHC (786-4), RDW (788-0), Platelets (777-3), MPV (32623-1), Differential (WBC subtypes)
• BMP/CMP: Sodium (2951-2), Potassium (2823-3), Chloride (2075-0), CO2 (1963-8), BUN (3094-0), Creatinine (2160-0), Glucose (2345-7), Calcium (17861-6), Albumin (1751-7), Total Protein (2885-2), ALP (6768-6), ALT (1742-6), AST (1920-8), Bilirubin Total (1975-2)
• Liver: ALT (1742-6), AST (1920-8), ALP (6768-6), GGT (2324-2), Bilirubin Total (1975-2), Bilirubin Direct (1968-7), Albumin (1751-7)
• Lipids: Total Cholesterol (2093-3), LDL (18262-6), HDL (2085-9), Triglycerides (2571-8), VLDL (13457-7)
• Thyroid: TSH (3016-3), Free T4 (3024-7), Free T3 (3026-2)
• Coagulation: PT (5902-2), INR (6301-6), aPTT (3173-2), Fibrinogen (3255-7), D-dimer (48066-5)
• Urinalysis: specific gravity (5811-5), pH (5803-2), protein (5804-0), glucose (5792-7), ketones (5797-6), blood (5794-3)

Step 4: Flag Abnormal Values

For each Observation:

1. Check interpretation.coding.code:
   • H = High, L = Low, HH = Critical High, LL = Critical Low, A = Abnormal
2. If no interpretation present, compare valueQuantity.value against referenceRange[0].low.value and referenceRange[0].high.value
3. Classify severity:
   • Normal: within reference range
   • Abnormal: outside reference range but not critical
   • Critical: matches critical value thresholds (see references/critical-values.md)
4. For critical values, prepend [CRITICAL] tag and include recommended immediate action

Step 5: Calculate Delta Checks

For each abnormal result, pull the prior value:

Tool: fhir_search
resourceType: "Observation"
queryParams: "patient=[patient-id]&code=[loinc-code]&_sort=-date&_count=5"

Calculate:

• Absolute change: current - previous
• Percent change: ((current - previous) / previous) * 100
• Rate of change per unit time

Flag significant deltas:

• Hemoglobin drop > 2 g/dL
• Potassium change > 1.0 mEq/L
• Creatinine increase > 0.3 mg/dL or > 50% from baseline (AKI criteria)
• Platelet drop > 50% (consider HIT if on heparin)
• Sodium change > 8 mEq/L in 24 hours (osmotic demyelination risk)

Step 6: Identify Abnormal Patterns and Differentials

Cross-reference abnormal values to detect clinical patterns:

• Elevated AST + ALT, AST/ALT > 2: alcoholic hepatitis pattern
• Elevated AST + ALT, AST/ALT < 1: non-alcoholic/viral hepatitis pattern
• Elevated ALP + GGT, normal AST/ALT: cholestatic pattern
• Elevated BUN/Creatinine ratio > 20: prerenal azotemia
• Low MCV + low ferritin: iron deficiency anemia
• High MCV + low B12 or folate: megaloblastic anemia
• Pancytopenia (low WBC + Hgb + Plt): bone marrow failure workup
• Elevated troponin + CK-MB: myocardial injury
• Elevated TSH + low Free T4: primary hypothyroidism
• Low TSH + high Free T4: hyperthyroidism
• Elevated anion gap: MUDPILES (Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates)

See references/lab-patterns.md for comprehensive pattern list.

Step 7: Correlate with Medications and Conditions

Tool: fhir_search
resourceType: "Condition"
queryParams: "patient=[patient-id]&clinical-status=active"

Tool: fhir_search
resourceType: "MedicationStatement"
queryParams: "patient=[patient-id]&status=active"

Common drug-lab interactions to check:

• Metformin + elevated lactate: lactic acidosis risk
• Statins + elevated CK/ALT: myopathy or hepatotoxicity
• ACE inhibitors + elevated potassium/creatinine: expected pharmacologic effect vs toxicity
• Warfarin + INR: therapeutic monitoring
• Lithium + renal function + thyroid: toxicity screening
• Heparin + platelet drop: HIT screening

Step 8: Format Output

LAB RESULTS INTERPRETATION -- [Patient Name] -- [Date Range]
=============================================================

CBC (collected [date])
  WBC:         8.2 x10^3/uL    [4.5-11.0]       NORMAL
  Hemoglobin:  9.1 g/dL        [12.0-16.0]       LOW [was 11.2 on MM/DD, delta -2.1]
  Hematocrit:  27.3%           [36.0-46.0]        LOW
  Platelets:   145 x10^3/uL   [150-400]          LOW (borderline)
  MCV:         72 fL           [80-100]           LOW

PATTERN: Microcytic anemia with dropping hemoglobin
  - Iron studies recommended to evaluate for iron deficiency
  - Delta check: Hgb dropped 2.1 g/dL -- clinically significant

BMP (collected [date])
  Potassium:   6.1 mEq/L      [3.5-5.0]         [CRITICAL] HIGH
    Immediate action: Verify specimen (check for hemolysis), obtain ECG,
    consider calcium gluconate if ECG changes present

[... additional panels ...]

CLINICAL CORRELATIONS
=====================
- Microcytic anemia: correlate with iron studies, consider GI evaluation
- Critical potassium: patient on lisinopril 20mg -- ACE inhibitor contributing factor
- Recommend: hold ACE inhibitor, repeat potassium stat, ECG

TRENDING SUMMARY
================
Hemoglobin: 12.1 -> 11.2 -> 9.1 (declining over 3 months)
Creatinine: 1.0 -> 1.1 -> 1.0 (stable)

Examples

Example 1: Routine Lab Review

User says: "Review labs for patient 55123 from the last month"

Actions:

1. fhir_read Patient/55123 -- returns 62-year-old male
2. fhir_search Observation?patient=55123&category=laboratory&date=ge[30-days-ago]&_sort=-date&_count=200 -- returns 18 Observations: CMP, CBC, lipid panel
3. fhir_search Observation?patient=55123&code=718-7&_sort=-date&_count=5 -- prior hemoglobin values for delta check
4. fhir_search Condition?patient=55123&clinical-status=active -- returns Type 2 DM, hypertension
5. fhir_search MedicationStatement?patient=55123&status=active -- returns metformin, lisinopril, atorvastatin

Result: Structured lab report showing CMP within normal limits, CBC with mild normocytic anemia (Hgb 11.8, stable from prior 11.9), lipid panel at goal on statin (LDL 68). Note: HbA1c 7.8% -- above ADA target for most adults. Recommend diabetes medication optimization. Correlate metformin with normal lactate. Atorvastatin with normal ALT/AST.

Example 2: Critical Value Detection

User says: "What do the latest labs show for patient emr-9981?"

Actions:

1. fhir_read Patient/emr-9981 -- returns 45-year-old female
2. fhir_search Observation?patient=emr-9981&category=laboratory&_sort=-date&_count=200 -- returns recent labs with potassium 2.4 mEq/L (interpretation: LL), sodium 118 mEq/L (interpretation: LL)
3. fhir_search Observation?patient=emr-9981&code=2823-3&_sort=-date&_count=5 -- prior potassium values
4. fhir_search Observation?patient=emr-9981&code=2951-2&_sort=-date&_count=5 -- prior sodium values
5. fhir_search MedicationStatement?patient=emr-9981&status=active -- returns furosemide, SSRI

Result:

[CRITICAL] Potassium: 2.4 mEq/L (ref 3.5-5.0) -- Critical low
  Prior: 3.8 mEq/L (2 weeks ago) -- delta -1.4 mEq/L
  Action: Obtain ECG stat, IV potassium replacement, hold furosemide
  Correlation: furosemide 40mg daily -- likely causative

[CRITICAL] Sodium: 118 mEq/L (ref 136-145) -- Critical low
  Prior: 134 mEq/L (2 weeks ago) -- delta -16 mEq/L
  Action: Assess volume status, check serum osmolality, urine sodium/osmolality
  Correlation: SSRI (sertraline) -- SIADH risk factor. Furosemide -- additional contributor
  Caution: Correct sodium no faster than 8 mEq/L per 24 hours (osmotic demyelination risk)

Example 3: Trend Analysis Request

User says: "Show me the creatinine trend for patient 7742 over the past year"

Actions:

1. fhir_read Patient/7742 -- returns 71-year-old male
2. fhir_search Observation?patient=7742&code=2160-0&date=ge[1-year-ago]&_sort=date -- returns 6 creatinine values over 12 months
3. fhir_search Condition?patient=7742&clinical-status=active -- returns CKD stage 3, hypertension, diabetes

Result:

CREATININE TREND -- Patient 7742 (71M, CKD Stage 3)
====================================================
2024-02: 1.4 mg/dL  (eGFR ~49)
2024-04: 1.5 mg/dL  (eGFR ~45)
2024-06: 1.6 mg/dL  (eGFR ~42)
2024-08: 1.5 mg/dL  (eGFR ~45)
2024-10: 1.8 mg/dL  (eGFR ~36)
2025-01: 2.1 mg/dL  (eGFR ~30)

Trajectory: declining eGFR, accelerating in last 3 months
Rate of decline: ~13 mL/min/1.73m2 per year (rapid, threshold >5)
Pattern: Progression from CKD Stage 3a to Stage 3b
Action: Nephrology referral, review nephrotoxic medications, check urine albumin

Troubleshooting

No Laboratory Observations Returned

• Confirm category=laboratory is supported by the FHIR server. Some servers use category=http://terminology.hl7.org/CodeSystem/observation-category|laboratory as the full system URL.
• Widen the date range. Default ge[30-days-ago] may miss infrequent labs.
• Search without category filter and inspect returned Observation categories to determine what values the server uses.

Observation Has No referenceRange

• Not all FHIR servers populate referenceRange. Fall back to standard reference ranges by age and sex from references/reference-ranges.md.
• Check if the Observation uses interpretation coding instead -- this may be the only abnormal flag available.

Panel Observations vs Individual Observations

• Some servers return panels as a single Observation with component array (e.g., CBC panel LOINC 58410-2 with WBC, RBC, etc. as components). Others return each analyte as a separate Observation.
• Check for hasMember references on panel-level Observations that point to individual result Observations.
• Always check both valueQuantity on the parent and component[].valueQuantity to capture all results.

Delta Check Returns Only One Value

• Patient may be new to the system. Note "no prior value available for comparison" and skip delta calculation.
• Try extending _count parameter or removing date filter to find historical values.

Related Skills

• critical-value-alert-generator -- for structured critical value alerting and notification workflows
• diabetes-panel-review -- for focused diabetes lab interpretation with ADA guideline application
• renal-function-dashboard -- for comprehensive renal function assessment and CKD staging
• preoperative-lab-checklist -- for evaluating lab readiness before surgical procedures

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