Shortened Elimination Diet Trial in Dogs

In the Literature

Fischer N, Spielhofer L, Martini F, Rostaher A, Favrot C. Sensitivity and specificity of a shortened elimination diet protocol for the diagnosis of food-induced atopic dermatitis (FIAD). Vet Dermatol. 2021;32(3):247-e65.

The Research …

Historically, an 8-week elimination diet trial with a hypoallergenic diet has been the gold standard to diagnose or rule out food-induced atopic dermatitis (FIAD), but this 8-week duration is often burdensome for pet owners and can be an obstacle in diagnosing food allergy. A recent study demonstrated that a shorter elimination diet trial may be possible with initial administration of prednisolone.¹ 

The current study aimed to assess the sensitivity and specificity of a shortened elimination diet trial in dogs after initial administration of either prednisolone or oclacitinib. All dogs were started on a single-protein or hydrolyzed diet. Of the 58 dogs that completed the study, 39 received prednisolone for 2 to 3 weeks and 19 received oclacitinib for 3 weeks. Medications were then discontinued. After a 2-week period without medication, each dog was fed their original diet. 

If relapse occurred after medication was discontinued, the same medication was administered for an additional week. In patients in which relapse occurred a second time, an additional week of the same medication was administered. All dogs that did not relapse were monitored for 2 weeks before being fed the regular diet. A diagnosis of FIAD was made if relapse did not occur without medication but did occur following dietary challenge. 

Of the dogs treated with prednisolone, 21 were determined to be food allergic; 14 of these dogs did not relapse after prednisolone was initially stopped, 6 dogs relapsed once, and one dog relapsed twice. Of the dogs treated with oclacitinib, 11 were determined to have FIAD; 7 of these dogs did not relapse after oclacitinib was initially stopped, and 4 dogs relapsed twice. 

For the purposes of this study, food allergy was ruled out if a dog relapsed more than once. Based on this threshold, sensitivity of the prednisolone and oclacitinib protocol was 95%  and 63%, respectively, and specificity for diagnosing FIAD was 100% for both medications.

… The Takeaways

Key pearls to put into practice:

• Elimination diet trials are frequently burdensome to owners, partly due to trial duration. This study suggests that treating clinical signs during the initial 2 to 3 weeks of the trial (with additional treatments if relapse occurs) can shorten trial time. Prednisolone administration during the initial diet trial is associated with a higher sensitivity for excluding diagnosis of food allergy.

• Elimination diet trials should be performed appropriately by using a veterinary therapeutic diet with either a hydrolyzed or novel protein. Table scraps, treats, and many flavored medications are not allowed during the elimination diet trial.

• Elimination diet trial remains the only way to definitively diagnose or exclude FIAD. Serum allergy tests for food are unreliable and not recommended. It is also important to remember that a positive serum allergy test is not diagnostic for environmental allergy, which can only be diagnosed by excluding other causes of pruritus.