Drug allergy laboratory findings: Difference between revisions

Jump to navigation Jump to search
Line 21: Line 21:
*[[Intradermal]] tests – these tests involve the injection of a small amount of allergen under the skin, into the dermis. [[Intradermal]] testing with delayed readout is more sensitive than a patch test, but carries a slightly higher risk of adverse allergic reactions when compared to skin testing. It tests for the same compounds as a skin prick test, and also leads to the diagnosis of IgE mediated hypersensitivity reactions. A prick test should be done beforehand, and the concentration used should be non-irritating.
*[[Intradermal]] tests – these tests involve the injection of a small amount of allergen under the skin, into the dermis. [[Intradermal]] testing with delayed readout is more sensitive than a patch test, but carries a slightly higher risk of adverse allergic reactions when compared to skin testing. It tests for the same compounds as a skin prick test, and also leads to the diagnosis of IgE mediated hypersensitivity reactions. A prick test should be done beforehand, and the concentration used should be non-irritating.
* [[In-vitro]] tests for immediate drug reactions are available, but are largely considered investigational.
* [[In-vitro]] tests for immediate drug reactions are available, but are largely considered investigational.
*Patch testing – this type of testing is useful for the diagnosis of various delayed type IV [[cutaneous]] reactions such as [[exanthemata]], [[acute generalized exanthematous pustulosis]], and [[flexular exanthema]]. It involves placing an aluminum disc containing allergens mixed with petrolatum on a patient’s back for 48 hours. The patient is then assessed for any reactions that may have occurred. This type of testing is not helpful to the diagnosis of [[Stevens-Johnson syndrome]] or [[toxic epidermal necrolysis]] and is contraindicated in anyone with a history of these conditions.
*Patch testing – this type of testing is useful for the diagnosis of various delayed type IV [[cutaneous]] reactions such as [[exanthemata]], acute generalized exanthematous pustulosis, and flexular exanthema. It involves placing an aluminum disc containing allergens mixed with petrolatum on a patient’s back for 48 hours. The patient is then assessed for any reactions that may have occurred. This type of testing is not helpful to the diagnosis of [[Stevens-Johnson syndrome]] or [[toxic epidermal necrolysis]] and is contraindicated in anyone with a history of these conditions.
*[[Skin biopsy]] may be useful to distinguish between Stevens-johnson syndrome and toxic epidermal necrolysis, and also to rule out other conditions on the differential diagnosis list.
*[[Skin biopsy]] may be useful to distinguish between Stevens-johnson syndrome and toxic epidermal necrolysis, and also to rule out other conditions on the differential diagnosis list.
*[[Histamine]] and [[tryptase]] levels- these test have shown to be useful in confirming the diagnosis of acute [[IgE]] mediated reactions, in particular [[anaphylaxis]]. Negative results do not rule out an anaphylactic reaction.

Revision as of 19:33, 20 August 2012


Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Charmaine Patel, M.D. [2]

Drug Allergy

Home

Patient Information

Overview

Classification

Pathophysiology

Causes

Differentiating Drug allergy from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Drug allergy laboratory findings On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Drug allergy laboratory findings

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Drug allergy laboratory findings

CDC on Drug allergy laboratory findings

Drug allergy laboratory findings in the news

Blogs on Drug allergy laboratory findings

Directions to Hospitals Treating Drug allergy

Risk calculators and risk factors for Drug allergy laboratory findings

Overview

Drug allergy and its associated conditions is primarily a clinical diagnosis based on the patient history, and through physical exam. Certain laboratory findings may be seen during the acute phase of the reaction, but are not always specific. Skin testing and biopsies can be performed when there is not a clear diagnosis.

Laboratory Findings

  • Erythrocyte sedimentation rate (ESR) may be increased.
  • White blood cell (WBC) may be increased.
  • Urine eosinophils may be increased, especially in cases of allergic interstitial nephritis.
  • Blood eosinophils may be increased, especially in cases of drug induced TEN.
  • Liver function tests (LFT)'s may be increased.
  • Elevations in tryptase may be seen detected in serum or plasma within several hours after an acute allergic event, and is consistent with anaphylaxis.
  • Histamine levels may be elevated after an acute reaction, but is unreliable for diagnosis.

Other Tests

  • Skin testing- skin prick testing (SPT) pricks the skin with a tiny amount of the suspected allergen, and leads to the diagnosis of IgE mediated type I hypersensitivity reactions. These tests are standardized for penicillin, and are also useful for local anesthetics, muscle relaxants. These tests are also very sensitive for high-molecular-weight protein substances such as insulin and monoclonal antibodies. A negative test is useful for ruling out a penicillin allergy, however with other tests (except for with high-molecular-weight proteins), a negative test is not always useful for ruling out the presence of serum specific IgE.
  • Intradermal tests – these tests involve the injection of a small amount of allergen under the skin, into the dermis. Intradermal testing with delayed readout is more sensitive than a patch test, but carries a slightly higher risk of adverse allergic reactions when compared to skin testing. It tests for the same compounds as a skin prick test, and also leads to the diagnosis of IgE mediated hypersensitivity reactions. A prick test should be done beforehand, and the concentration used should be non-irritating.
  • In-vitro tests for immediate drug reactions are available, but are largely considered investigational.
  • Patch testing – this type of testing is useful for the diagnosis of various delayed type IV cutaneous reactions such as exanthemata, acute generalized exanthematous pustulosis, and flexular exanthema. It involves placing an aluminum disc containing allergens mixed with petrolatum on a patient’s back for 48 hours. The patient is then assessed for any reactions that may have occurred. This type of testing is not helpful to the diagnosis of Stevens-Johnson syndrome or toxic epidermal necrolysis and is contraindicated in anyone with a history of these conditions.
  • Skin biopsy may be useful to distinguish between Stevens-johnson syndrome and toxic epidermal necrolysis, and also to rule out other conditions on the differential diagnosis list.
  • Histamine and tryptase levels- these test have shown to be useful in confirming the diagnosis of acute IgE mediated reactions, in particular anaphylaxis. Negative results do not rule out an anaphylactic reaction.