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Hereditary angioedema: Suspect-and-test checklist for clinicians

A one-page worksheet that turns the full Hereditary angioedema diagnosis guide into something you can use at the point of care: what to look for, what to order, which results should not end the workup, and who else to test or refer.

Who it is forClinicians and care teams who may see Hereditary angioedema before it is diagnosed, including primary care, the specialists named in the guide, and referral or genetics coordinators.
When to use itWhen Hereditary angioedema is on the differential, when a patient has several red flags, or when you are preparing a referral or a second opinion.

How to use it, section by section

  1. Red flags present: Tick each finding the patient has. They are grouped by body system so you can scan quickly.
  2. Already labeled as: Tick earlier diagnoses on the chart that the sources say are often given first.
  3. Family to test: Note relatives who may need testing, and record when symptoms began and which specialists have already been seen.
  4. Testing, in order: Tick each test as you order it and write the result on its line. The order follows the published sources.
  5. Results that do not rule it out: A reminder of findings that can look reassuring but do not exclude Hereditary angioedema.
  6. Specialists: Tick the referral, then write who it went to and any notes.
Two ways to fill it inPrint it blank and write on it, or tick boxes and type on this screen first, then print or save as a PDF. Keep it with the chart or send it with the referral.
PrivacyNothing you type is sent or saved. It stays in this browser tab and disappears when you close it. Use patient initials, not full identifiers.

What it is not: Not a diagnostic score, a protocol or coding advice. It summarizes published sources, and clinical judgment and the treating clinician govern. Every point is sourced in the full Hereditary angioedema guide.

One Letter page. Use your browser's print or save as PDF.Full guide with sources
Suspect-and-test checklist
Hereditary angioedema

Autosomal dominant. Recurrent swelling without wheals that does not respond to antihistamines, steroids or epinephrine.

ICD-10-CMD84.1Trial Friend for Clinicians

1Red flags present

Swelling

Abdomen and airway

Course and triggers

Family

2Already labeled as

3Family to test

4Testing, in the order the sources describe

  1. C4, C1-INH protein and C1-INH functionAll 3 together in every suspected patient; repeat positive results to confirm.
    Result
  2. Read the patternType 1: low protein and function. Type 2: normal or high protein, function under 50%.
    Result
  3. Chromogenic functional assayMore sensitive than ELISA per US HAEA; handle and process samples promptly.
    Result
  4. C1qWAO/EAACI: onset after 30 without family history. US HAEA: onset after 40. Low C1q suggests acquired deficiency.
    Result
  5. Gene testing with normal C1-INHF12, ANGPT1, PLG, KNG1, MYOF, HS3ST6. SERPING1 only in selected cases.
    Result
  6. Infants of an affected parentC4 unreliable under 12 months; cord blood can read low; repeat after age 1.
    Result

5Results the sources say do not rule it out

  • Normal C1-INH protein. Type 2 has normal or high protein with low function.
  • A single normal C4. Guidelines differ on it as a screen; WAO/EAACI advises against using it alone.
  • Wheals present. Chronic urticaria can coexist with HAE.
  • No family history. Up to 25% of patients have none.

6Specialists the sources name

Diagnosis code: D84.1 Defects in the complement systemCodes patients often carry before diagnosis are listed in the online guide.
Full guide and sourcesEvery point here is sourced in the online guide, which also has a patient note to print.
Trial Friend, trialfriend.com/for-clinicians. Key sources: WAO/EAACI guideline (2022); US HAEA guideline (2020); European diagnostic delay study (2013); Icatibant Outcome Survey misdiagnosis analysis (2016); Pediatric onset and delay study (2015); Swelling pattern study (2006); all 13 with links in the online guide. Checked November 10, 2026. A reference checklist for licensed clinicians that summarizes published sources. It is not a diagnostic tool, a score or a protocol, and it does not replace clinical judgment, local practice or the prescribing information. Not coding advice. Trial Friend never receives anything written or typed on this sheet.