title: Factors associated with negative histamine control for penicillin allergy skin testing in the inpatient setting.
abstract: BACKGROUND
  Identification of factors adversely affecting the utility of allergy skin testing is important in optimizing patient care. Inpatient penicillin skin test data from 1997 through 2007 demonstrate that up to 20% of attempted penicillin skin tests are indeterminate owing to a negative histamine test response, despite exclusion of H1 antagonists. Critical illness, vasopressors, steroid use, and psychotropic medications have been postulated to influence outcomes, but large studies are lacking.
  
  
  OBJECTIVE
  To identify factors associated with a negative histamine test response for the inpatient setting.
  
  
  METHODS
  Fifty-two cases were identified with a negative histamine response after penicillin skin testing in the absence of antihistamine therapy for 72 hours before testing. One hundred twenty-five controls with a normal histamine response were randomly selected from same population. Independent variables assessed included stay in the intensive care unit (ICU), skin color, diabetes, age, use of vasopressors, H2 blocker, steroids, other immunosuppressive drugs, thyroid replacement, proton pump inhibitors, diuretics, 5 categories of psychotropic medications, and amiodarone.
  
  
  RESULTS
  Mean age was 68 years for cases vs 60 years for controls (P = .002). Bivariate analysis showed ICU stay was more frequent in cases than in controls (73.1% vs 33.6%, P < .001). Regression analysis yielded odds ratios (ORs) of 8.18 (95% confidence interval 3.22-20.76) for ICU status, 3.76 (1.30-10.92) for systemic corticosteroids, and 4.90 (1.17-20.62) for H2 blockers as associated with lack of histamine response. For every additional year in age, there was increase in the OR of 1.04 (1.01-1.07).
  
  
  CONCLUSIONS
  Regression analysis supports ICU stay during skin testing as associated with a high OR for a negative histamine response independent of age. Systemic corticosteroids, H2 blockers, and older age are associated with a significant OR for a negative histamine response. This is one of largest studies on factors associated with a negative histamine response for the inpatient setting and has significant implications for clinical practice.
authors.affiliation: Clinical Immunology and Allergy, University of California-Los Angeles, Los Angeles, California. Electronic address: BGeng@mednet.ucla.edu.
authors.forename: Bob
authors.initials: B
authors.lastname: Geng
authors.affiliation: Department of Medicine, University of California-Los Angeles, Los Angeles, California.
authors.forename: Ami
authors.initials: A
authors.lastname: Thakor
authors.affiliation: Department of Medicine, University of California-Los Angeles, Los Angeles, California.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Clayton
authors.affiliation: Division of Allergy and Immunology, National Jewish Health and Division of Allergy, Asthma and Clinical Immunology, University of Colorado, Denver, Colorado.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Finkas
authors.affiliation: Division of Rheumatology, Allergy and Immunology, University of California-San Diego, La Jolla, California.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Riedl
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D016022:Case-Control Studies; D003920:Diabetes Mellitus / Q000276:immunology; D003951:Diagnostic Errors; D004232:Diuretics / Q000494:pharmacology; D004342:Drug Hypersensitivity / Q000175:diagnosis* / Q000209:etiology; D005188:False Negative Reactions; D005260:Female; D006632:Histamine; D006635:Histamine H2 Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D065386:Historically Controlled Study; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007297:Inpatients; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010406:Penicillins / Q000009:adverse effects* / Q000276:immunology; D011619:Psychotropic Drugs / Q000494:pharmacology; D012372:ROC Curve; D012189:Retrospective Studies; D012494:Sampling Studies; D012880:Skin Pigmentation; D012882:Skin Tests; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000305:Adrenal Cortex Hormones; D004232:Diuretics; D006635:Histamine H2 Antagonists; D007166:Immunosuppressive Agents; D010406:Penicillins; D011619:Psychotropic Drugs; D014662:Vasoconstrictor Agents; D006632:Histamine