Patch Test Reading Documentation: An ICDRG Checklist for Allergy Practices

The short answer: a well-documented patch test records four things. **What

was applied** (series, allergens, chambers, site map) and what could blunt the

result. Each reading, with its date and time and an ICDRG grade for every

site, including negatives. The interpretation: irritant or allergic, and the

clinical relevance of each positive. The counselling: which allergens to

avoid and where they're found.

The checklist below follows *Contact Dermatitis: A Practice Parameter, Update

2015* from the Joint Task Force on Practice Parameters (AAAAI, ACAAI and the

Joint Council of Allergy, Asthma & Immunology; Fonacier L, et al. J Allergy Clin

Immunol Pract 2015;3:S1-39). Its Summary Statement 19 says to "read and

interpret PT conforming to the scoring system developed by the International

Contact Dermatitis Research Group." Summary Statement 20 says to "remove and

read PT at approximately 48 hours after application," with a second reading

"between 3 and 7 days following application."

It's a documentation aid, not a protocol. Your practice's own patch-test

procedure, signed off by your allergists, comes first.

The ICDRG grading scale

The parameter reproduces the scale the ICDRG published in 1970, which "continues

to be widely used":

| Grade | Meaning |

|---|---|

| − | Negative reaction |

| ?+ | Doubtful reaction, faint erythema only |

| 1+ | Weak positive: nonvesicular erythema, infiltration, possibly papules |

| 2+ | Strong positive: vesicular erythema, infiltration and papules |

| 3+ | Extreme positive: intense erythema and infiltration, coalescing vesicles, bullous reaction |

| IR | Irritant reaction |

| NT | Not tested |

Record a grade for every site at every reading, not only the positives. A grid

that shows "−" at 48 hours and "1+" at the second reading tells the next reader

something a blank cell doesn't.

Checklist 1: before application

```

PATCH TEST: APPLICATION

Indication

• Presenting dermatitis: [site(s), duration, pattern]
• Suspected exposures: [personal products, occupation, hobbies, footwear, medications]

What was applied

• Series: [baseline / supplemental series / patient's own products]
• Number of allergens: [ ] Chamber system: [ ]
• Site map: [back, left/right, rows/columns, marked with ___]
• Patient-brought products: [list, concentration, vehicle]

Things that can blunt the result (document each)

• Systemic corticosteroids / immunosuppressants: [none / drug, dose]
• Topical corticosteroid or calcineurin inhibitor on the test site: [none / last use]
• Recent UV exposure to the back (sun, tanning): [Y/N]
• Active dermatitis on the test site: [Y/N]

Instructions given

• Patch care per practice handout: [given Y/N]; return for readings on [dates]

```

Why this matters: Summary Statement 16 advises avoiding or reducing

systemic immunosuppressants before testing and avoiding topical

corticosteroids, calcineurin inhibitors or UV light on the test site, "because

these may reduce allergic PT responses." Summary Statement 22 lists these among

the causes of false negatives. If a reading is negative, the note should show

whether any of them applied.

Checklist 2: each reading

```

PATCH TEST: READING [1 / 2 / late]

Date and time: [ ] Hours since application: [ ]

Patches removed at: [ ] (reading 1)

Read by: [ ]

Site | Allergen | Grade (−, ?+, 1+, 2+, 3+, IR, NT) | Notes

1 | [ ] | [ ] | [ ]

2 | [ ] | [ ] | [ ]

...

Loose or nonadherent chambers: [none / which]

Photos taken: [Y/N, which sites]

Morphology notes: [pustular / edge effect / pressure reaction / crescendo vs decrescendo]

```

Three details worth writing down:

• The timing. The parameter recommends the first reading at about 48 hours,

when the patches come off, and a second between days 3 and 7. It notes that

some allergens (it lists metals, neomycin and topical corticosteroids among

them) tend to peak late, and that a late reading may be needed for some

contactants. Record the actual hours since application at each reading.

• Crescendo or decrescendo. The parameter notes that some irritant

reactions seen in the first 48 hours tend to fade by 96 hours (a decrescendo

effect). A reaction that grows between readings reads differently from one

that fades. Two graded readings side by side make that visible.

• Possible false positives. Summary Statement 21 lists irritants, pressure

from the chamber, "angry back" and testing on active dermatitis. It also

notes that a pustular reaction to metals in atopic patients is frequently

irritant. If you graded a site IR or ?+, say why in the notes column.

Checklist 3: interpretation and counselling

```

PATCH TEST: INTERPRETATION

Positive reactions

Allergen | Best grade | Reading | Relevance (current: definite / probable / possible; past; unknown) | Exposure source

[ ] | [ ] | [ ] | [ ] | [ ]

Irritant or doubtful reactions: [list, reason]

Negative result: [any factor that may have caused a false negative]

Further testing considered: [ROAT / use test / repeat test / none]

Counselling

• Allergens to avoid: [ ]
• Where they are found / cross-reactions discussed: [ ]
• Written avoidance list or safe-product list given: [Y/N]
• Follow-up: [ ]

```

Why relevance gets its own column: Summary Statement 23 says to "determine

the relevance of a PT result based on the clinical and exposure history." The

parameter defines current relevance as definite if a test with the suspected

material is positive, probable if the allergen is in known skin contactants

and the presentation fits, and possible if contact with materials known to

contain it was likely; past relevance means the exposure was in the past. A

positive grade without a relevance call leaves the next clinician to redo the

history.

Counselling closes the loop. Summary Statement 42 says that once the

allergen is identified, the patient "should be counseled on avoidance of

contact with the offending agent and informed of any cross-reactivity

concerns." Note which allergens, which sources and what written material the

patient left with.

Where patch-test documentation usually breaks

A patch test spans several visits over most of a week. The application, the

48-hour grid, the second reading and the photos often end up on a paper grid,

in a photo folder and in separate notes, and the clinician stitches them back

together before signing.

Medora was built with a working allergy practice to keep that in one place:

• Medora supports the patch-testing workflow: ordering, the 48-hour and Day

3–4 readings scored on the ICDRG scale, photos, and clinician sign-off, in

one record.

• Patch testing lives in the same patient record as the allergy note and skin

testing, so the interpretation visit can see what was recorded at each

reading.

• Medora Copilot listens to the interpretation visit and drafts an

allergy-structured SOAP note, including the counselling discussed, for the

clinician to review.

• The grades are entered by your staff. Medora doesn't read or grade patch

tests from photos, and the clinician reviews, edits and signs every note.

In a 60-day pilot at Allergy Affiliates, provider sign-off per skin-test visit went from 18 minutes to 4

(the case study).

Frequently asked questions

What is the ICDRG patch test grading scale?

The International Contact Dermatitis Research Group scale grades each patch

test site as negative (−), doubtful (?+, faint erythema only), weak positive

(1+), strong positive (2+), extreme positive (3+), irritant reaction (IR) or

not tested (NT). The AAAAI/ACAAI contact dermatitis practice parameter

recommends reading patch tests with this scale.

When should patch tests be read?

The 2015 practice parameter recommends removing and reading the patches at

about 48 hours after application, and doing a second reading between days 3

and 7. Some allergens, including metals, neomycin and topical corticosteroids,

may need a later reading. Follow your practice's protocol.

How do you document clinical relevance of a positive patch test?

Correlate each positive with the patient's exposure history. The parameter

classes current relevance as definite, probable or possible, and separates

past relevance (positive, but the exposure was in the past). Record the

relevance and the likely exposure source next to each positive.

What should a patch test note say about a negative result?

Whether anything could have caused a false negative: systemic corticosteroids

or immunosuppressants, topical steroids or calcineurin inhibitors on the test

site, recent UV exposure, loose chambers, or a missed late reading. The

parameter lists these in Summary Statements 16 and 22.

Does Medora read patch tests from photos?

No. Staff score each site on the ICDRG scale in Medora, photos are stored

with the readings, and the clinician signs. Medora Copilot drafts the visit

note for the clinician to review, edit and sign.

Try it on your own visits

• See how Medora handles allergy documentation
• Start the 14-day free trial of Medora Scribe (no card needed)
• Book a demo
• Read the full buyer's guide
• The skin-test documentation checklist
• The allergy ICD-10 coding guide

*Source: Fonacier L, Bernstein DI, Pacheco K, et al. Contact Dermatitis: A

Practice Parameter, Update 2015. J Allergy Clin Immunol Pract.

2015;3(3 Suppl):S1-39 (doi:10.1016/j.jaip.2015.02.009; Summary Statements 16

and 19–23 and 42, the glossary, Figure 1 and Table II). Quotes are from the

parameter. Check for later updates and follow your own protocols.*