Filling a Prescription for an Epinephrine Autoinjector, Visits to an Allergist or Immunologist among Preventive Factors that Reduce the Risk of Severe Anaphylaxis

July 3, 2014
Andrew Smith

Analysis of emergency department cases indicates that anaphylaxis severity increases with age and other health problems, but preparations can reduce the danger to patients.

Analysis of emergency department (ED) cases indicates that anaphylaxis severity increases with age and other health problems, but preparations can reduce the danger to patients.

The team behind the new study, which was published in The Journal of Allergy and Clinical Immunology, reviewed the medical records of 11,972 people who sought ED care for anaphylaxis. The researchers then separated the 2,622 (22%) cases that were severe enough to merit hospitalization from the others and looked for factors that increased or decreased the likelihood of a severe attack.

The largest risk factors uncovered by multivariable analysis were ED visits or hospitalizations for any cause during the 12-month period preceding each patient’s allergic attack. Prior ED visits increased the risk of severe anaphylaxis by 18% (95% confidence interval [CI]: 1.07 to 1.30). Prior hospitalization increased the risk by 55% (95% CI: 1.36 to 1.75).

The largest mitigating factors were visits to either an allergist or an immunologist or the acquisition of an epinephrine autoinjector (EAI) at any time in the 12 months before each patient’s attack. The first reduced risk of severe anaphylaxis by 22% (95% CI, 0.63 to 0.95), while the second reduced risk by 36% (95% CI, 0.53 to 0.78).

The study largely agrees with older research about which factors increase the risk of severe anaphylaxis. A large 2013 study that used data from eight Australian EDs, for example, identified older age and lung disease as the biggest risks.

However, there were several differences. The Australian study found that anaphylaxis caused by medication was more likely to be severe compared with anaphylaxis caused by food or stings. The new study, on the other hand, found that medications and stings triggered severe anaphylaxis in roughly equal percentages but that attacks triggered by food were significantly less likely to be severe.

The authors of the current study noted that some differences were to be expected, as previous research has used various definitions of “severe” anaphylaxis and many different methodologies for tracing risk factors.

Sunday Clark, ScD, MPH, an assistant professor of healthcare policy and research at Weill Cornell Medical College in New York, led the study team, which acquired its patient records by searching two MarketScan Research Databases with an expanded diagnosis code algorithm from the International Classification of Diseases, Ninth Revision, Clinical Modification.

Then, to make sure they had enough patient data for analysis, Clark and her colleagues included only patients who had continuous medical and prescription coverage for at least one year before and after the visit date.

That process produced large enough patient numbers and strong enough statistics to provide valuable insight to caregivers, the researchers concluded.

“Pre-index preventive anaphylaxis care (ie, EAI prescription fill and allergist/immunologist visit) was associated with a significantly lower risk,” they wrote, “supporting the benefits of preventive anaphylaxis care in real-world practice.”

Such support is badly needed. Research has yet to answer some of the most basic questions about anaphylaxis, including how common it is (estimates vary more than 1500%). More complex questions about who, if anyone, should receive what type of preventative care likewise remain largely unanswered.