Diagnostic accuracy of an atopy patch test compared to a DBPCFC for detection of cow’s milk allergy

StudyPopulation testedPrevalenceDiagnostic accuracy for cow’s milkComments
Positive test on challengeImmediate reactionDelayed reactionBoth immediate & delayedSensitivity (%)Specificity (%)PPV (%)NPV (%)
Isolauri 1996161

EL=DS III
183 children aged 2–36 months with atopic eczema, not selected on basis of suspected allergy to cow’s milk, although ‘most’ excluded egg from their diet.54% on DB (and open) challenge

0 for placebo challenge
49%51%NR61 (59 on open challenge)81 (83 on open challenge)NRNRNo cow’s milk taken 1 month before test (they were breastfed (11%), or given soya milk 39%, whey formula 24%, or amino-acid formula 26%).

Antihistamines discontinued for 3 days–6 weeks before test.
It is not stated whether the eczema was clear/controlled before the test

Food challenges:
Placebo: amino-acid derived substitute (Neocate).
Test preparation: same as placebo + skimmed cow milk powder. 1-week challenge period; follow-up at weeks 1 and 2. A positive reaction to the food challenge was defined as an ‘unequivocal adverse reaction to challenge’

Humidified skimmed cow milk used for patch testing; left under occlusion for 48 hours and read 15 minutes after removing the patch, and at 72 hours. Reactions classified into four groups (negative, irritation, significant erythema, and erythema with oedema or eczema).

Subsequent open challenge showed a 1% false negative of DB challenge.

It is unclear whether food challenge was done blind to the results of the patch test.

Unknown whether the sensitivity and specificity data represent those who had either or both immediate or delayed reactions
Roehr 2001165

EL=DS III
98 children aged 2 months to 11.2 years with atopic eczema (62% mild, 28% moderate and 10% severe). Not stated whether they were suspected of having food allergy.55%
(64% milk, 67% egg, 51% wheat, 16% soya)

(placebo challenge results NR)
49%26%
All atopic eczema
25%
All atopic eczema plus respiratory or gastrointes tinal symptoms
47 (any reaction)96 (any reaction)95 (any reaction)51 (any reaction)Antihistamines discontinued 72 hours before test. TCS (hydrocortisone 1% or betamethasone 0.1%) were permitted twice daily.
It is not stated whether the eczema was clear/controlled before the test

Food challenges:
Placebo: amino-acid derived substitute (Neocate).
Test preparation: 173 food challenges were undertaken; 41% with cow’s milk, 24% with hen’s egg, 20% with wheat and 15% with soya. Successive, increasing, doses of these foods were administered every 20 minutes. Challenges were stopped if clinical symptoms were observed or the maximum dose had been reached.
Children were observed for 48 hours as inpatients. A positive reaction to the food challenge was noted if one of the following occurred: urticaria, angioedema, wheezing, vomiting, diarrhoea, abdominal pain, shock, or exacerbation of eczema. An early reaction was that occurring within 2 hours, and a delayed reaction occurred after 2 hours.

Patch test: one drop fresh cow’s milk, whisked egg (white and yolk), wheat powder, and soya milk. Site checked for immediate reactions after 20 minutes, then left under occlusion for 48 hours and read 20 minutes after removing the patch, and at 72 hours. A positive reaction was defined as erythema with infiltration. Irritant reactions (sharply defined brownish erythema, decrescendo phenomenon, blistering and lack of clear infiltration) were regarded as negative.

It is unclear whether food challenge was done blind to the results of the other tests.
26 (immediate reaction)96 (immediate reaction)88 (immediate reaction)56 (immediate reaction)
78 (delayed reaction)96 (delayed reaction)93 (delayed reactio86 (delayed reaction
Mehl 2006181437 consecutive referrals for suspected food allergy. Children aged 3 months – 14 years (median=13 months). 90% had AE49% (n=341) (DB and open challenge)31958660Open challenges were allowed in children <1 year with history of immediate-type reactions. 77% of challenges were double blind.

>1 week elimination diet required before provocation

Eczema was clear before testing.

Hydrocortisone (1%) or betamethasone (0.01%) permitted twice daily. Advice to stop antihistamines 72 hours before provocation.

NR=not reported

From: Evidence tables

Cover of Atopic Eczema in Children
Atopic Eczema in Children: Management of Atopic Eczema in Children from Birth up to the Age of 12 Years.
NICE Clinical Guidelines, No. 57.
National Collaborating Centre for Women's and Children's Health (UK).
London: RCOG Press; 2007 Dec.
Copyright © 2007, National Collaborating Centre for Women’s and Children’s Health.

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