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Anaphylaxis diagnosis must be established rapidly in a clinical setting, especially given the sudden and critical nature of the event. Laboratory tests play a limited role in diagnosis. The diagnosis relies on the patient's history and physical examination findings, guided by widely accepted clinical criteria.
Patient history is the first and most critical step in diagnosing anaphylaxis and determining its potential causes. When taking a history, the time of onset, progression, duration of the event, observed symptoms, any treatments administered (at home or in a hospital), and potential triggers/allergens should be thoroughly investigated.
In clinical practice, anaphylaxis should be suspected if there is an acute onset of two or more findings involving the skin, respiratory, circulatory, and gastrointestinal systems. However, a significant factor that can lead to missed diagnoses is that skin findings are not always present.
Therefore, clinical criteria have been established to support the diagnosis of anaphylaxis. The presence of any of the following three criteria makes the likelihood of anaphylaxis very high:
1. Acute onset (minutes to hours) of symptoms involving the skin, mucous membranes, or both (e.g., generalized urticaria, pruritus, flushing, angioedema of lips/tongue/uvula) AND at least one of the following:
a. Respiratory difficulty or compromise
b. A drop in blood pressure or symptoms associated with end-organ dysfunction
2. Rapid onset (minutes to hours) of two or more of the following after exposure to a likely allergen for the patient:
a. Symptoms involving the skin, mucous membranes, or both (e.g., generalized urticaria, pruritus, flushing, angioedema of lips/tongue/uvula)
b. Respiratory difficulty or compromise
c. A drop in blood pressure or symptoms associated with end-organ dysfunction
d. Persistent gastrointestinal symptoms (e.g., crampy abdominal pain, vomiting)
3. A drop in blood pressure after exposure to a known allergen for the patient (minutes to hours):
a. In infants and children: Low systolic blood pressure for age or a >30% decrease in systolic blood pressure from baseline.
b. In adults: Systolic blood pressure below 90 mmHg or a >30% decrease from the patient's baseline.
How is Anaphylaxis Diagnosed?
Patient history is the first and most critical step in diagnosing anaphylaxis and determining its potential causes. When taking a history, the time of onset, progression, duration of the event, observed symptoms, any treatments administered (at home or in a hospital), and potential triggers/allergens should be thoroughly investigated.
In clinical practice, anaphylaxis should be suspected if there is an acute onset of two or more findings involving the skin, respiratory, circulatory, and gastrointestinal systems. However, a significant factor that can lead to missed diagnoses is that skin findings are not always present.
Therefore, clinical criteria have been established to support the diagnosis of anaphylaxis. The presence of any of the following three criteria makes the likelihood of anaphylaxis very high:
1. Acute onset (minutes to hours) of symptoms involving the skin, mucous membranes, or both (e.g., generalized urticaria, pruritus, flushing, angioedema of lips/tongue/uvula) AND at least one of the following:
a. Respiratory difficulty or compromise
b. A drop in blood pressure or symptoms associated with end-organ dysfunction
2. Rapid onset (minutes to hours) of two or more of the following after exposure to a likely allergen for the patient:
a. Symptoms involving the skin, mucous membranes, or both (e.g., generalized urticaria, pruritus, flushing, angioedema of lips/tongue/uvula)
b. Respiratory difficulty or compromise
c. A drop in blood pressure or symptoms associated with end-organ dysfunction
d. Persistent gastrointestinal symptoms (e.g., crampy abdominal pain, vomiting)
3. A drop in blood pressure after exposure to a known allergen for the patient (minutes to hours):
a. In infants and children: Low systolic blood pressure for age or a >30% decrease in systolic blood pressure from baseline.
b. In adults: Systolic blood pressure below 90 mmHg or a >30% decrease from the patient's baseline.