Lectura de parches para DXC

Published in Dermatology and 

1 other channel 

Journal Scan / Research · March 12, 2020

Ideal Time for Patch Test Reading

Dermatitis

TAKE-HOME MESSAGE

• Of 195 allergens (36,971 individual reactions), 142 allergens (72.8%) had different reactions on day 5 than on day 7 or later. While our current standard practice is to read on days 3 and 5 for most allergens, this may not be sufficient. Readings on both days 5 and 7 or later could have the highest yield for metals, acrylates, some preservatives, and topical antibiotics.

• The ideal timing for patch test reading has been debated. Delayed reactions occurred mostly with metals and acrylates, but also with some fragrances, preservatives, and topical antibiotics.

– InYoung Kim, MD, PhD

Written by

 

 

Christen Maria Mowad MD

The timing of patch test reading has been debated. It is clear that at a minimum of two readings are needed to avoid false positive or false negative reactions. The first reading is generally agreed upon at 48 hours. However, the most appropriate timing of the second reading remains variable from 72 hours to 168 hours or later.

Delayed reactions are observed most commonly with metals, some preservatives and neomycin. This study looked at discordant readings on day 5 and day 7 or later. A significant proportion of those read on day 5 would have been missed if only day 7 was performed and vice versus. Many of the late reacting allergens were acrylates and metals. This was a retrospective study which introduces some limitations to the findings. This was pointed out by the authors who stated that guided by prior studies they primarily perform delayed readings for series containing metals which often contain acrylates potentially overrepresenting these allergens in this study.

Clinical settings, patient availability and allergens tested are all considered when scheduling patch test readings This study suggests patch test reads at 48 hours and day 5 and day 7 provide the highest yield.   Further studies looking at all allergens and their positive reactions and concordance at days 5 and day 7 will better answer these questions for us. This study reminds us that if testing for metals, acrylates and some antibiotics, late readings may be needed.

Abstract

BACKGROUND

A major question in patch testing is when to perform the final reading. Our current standard practice is to place patches on day 1, remove them on day 3, and perform readings on days 3 and 5. For certain allergens, another reading is performed sometime from days 7 to 14.

OBJECTIVES

The aim of the study was to identify allergens with positive reactions on day 5 that were negative on day 7 or later and allergens with negative reactions on day 5 that were subsequently positive on day 7 or later.

METHODS

We reviewed records of patients who underwent patch testing from January 2007 to December 2016 at Mayo Clinic with readings on day 5 and day 7 or later.

CONCLUSIONS

In total, 131 allergens had positive reactions on day 5 that were negative on day 7 or later, and 58 allergens had negative reactions on day 5 that were positive on day 7 or later. Twenty-five allergens had significantly higher reaction rates on day 5 than day 7 or later. Our standard practice is to perform readings on days 3 and 5 and on days 3, 5, and 7 or later for series containing metals. Readings on days 3, 5, and 7 or later should also be considered for acrylates.

Dermatitis

The Final Patch Test Read: Day 5 or Day >7?

Dermatitis 2020 Jan 01;[EPub Ahead of Print], HM Cantwell, LA Drage, RA El-Azhary, MR Hall, JM Killian, JA Yiannias, MDP Davis