Patch Test Reading Research Articles

Patch test reading: a comparison between 2 application methods.

Patch test reading: a comparison between 2 application methods.

Contact allergy to ophthalmic dipivalyl epinephrine hydrochloride: demonstration by patch testing

A patient presented with a 3-month history of conjunctivitis and periocular eczema. He had a 3-year history of glaucoma and was being treated with 3 different locally applied eyedrops (Timoptic (timolol maleate) ophthalmic solution 0.25%, Pilocar (pilocarpine) ophthalmic solution 1%, and Propine (dipivalyl epinephrine hydrochloride) ophthalmic solution 0.1%). Patch testing with all 3 undiluted eyedrop solutions revealed a reaction only to Propine eyedrops. Patch testing to the individual components of Propine eyedrops revealed an allergic reaction to 0.5% dipivalyl epinephrine hydrochloride that was apparent on the 2nd patch test reading. After discontinuing the Propine eyedrops, the conjunctivitis as well as the periocular dermatitis resolved, proving that the positive patch tests were relevant to both. It was reported that re-exposure to dipivalyl epinephrine hydrochloride by intra-ocular challenge was necessary to diagnose this allergy. This is the first demonstration of dipivalyl epinephrine hydrochloride allergy by patch testing. Since the 1st patch test reading (2 days) was weak, 2nd patch test (4 days) readings may be important in diagnosing this allergy by patch testing.

Study of dose-response relationship in contact sensitivity using an in vitro assay.

Dose-response relationships in contact sensitivity were evaluated in guinea pigs using an in vitro assay. Guinea pigs were sensitized with different doses of 1-chloro-2,4-dinitrobenzene (DNCB) and challenged with DNCB and 2,4-dinitrobenzene sulfonic salt (DNBS). Lymph node cells from sensitized and control guinea pigs were cultured in the presence of different doses of DNCB and DNBS at 8 x 10(5) cells/well, respectively. The sensitivity was evaluated by the lymphocyte transformation test (LTT), which was assessed by uptake of 3H-thymidine. The results indicated that there were significant correlations between the doses of sensitizers and the values of LTT in both phases of induction and challenge. Thus, the presence of higher numbers of LTT-reactive lymphocytes in the circulation may well correlate with the sensitizing doses. The values examined by in vitro assay correlated well with patch test readings (r = 0.653), indicating that following the increment of degree of patch test reactions, the values of SI were also increased. The in vitro LTT may discriminate between positive patch test reactions and negative or doubtful reactions, but not between weak positive and strong positive reactions. The in vitro assay reproduced the cross-reaction between DNCB and DNBS which was confirmed in vivo.

Epidemiological survey of standard series patch test results and observations on day 2 and day 4 readings

Computer data on 4721 consecutive patients patch tested with an extended standard series were analysed for the frequency of allergic reactions to each substance. Particular attention was given to the negative first reading at day 2 (D2) which later became positive at day 4 (D4). A total of 4210 allergic reactions were recorded. 993 of which were negative on D2 (24%). The most frequent positive reactions were to nickel sulphate (18%), fragrance-mix (8%), colophony (6%), neomycin (6%), cobalt chloride (6%), thiuram-mix (4%) and potassium dichromate (3%). The frequency of negative D2, positive D4 readings was sizeable for all but one substance, primin, with a range of 14% for fragrance-mix to 64% for neomycin. All of 21 positive reactions to primin were recorded on D2. In our opinion, it is unjustified to perform D2-only patch test readings.

Chlorhexidine gluconate and acetate in patch testing

Patch testing to chlorhexidine is usually performed with chlorhexidine gluconate aq. We report the results of 297 patients, almost all with leg ulcers, concomitantly tested with chlorhexidine acetate 1% aq. and chlorhexidine gluconate 1% aq. 39 patients had positive reactions to one of these compounds or to both. 36 positive reactions to the acetate were found, in contrast to 18 reactions to the gluconate. The reactions were considered relevant in 22 of 39 patients, since these patients had developed an eczema in an area where a chlorhexidine compound was used, and discontinuing the chlorhexidine compound resulted in improvement of the condition. In 10 of these 22 patients, the diagnosis would have been missed if the gluconate only had been used for testing, while the acetate failed to diagnose 2 patients. In 109 patients without leg ulcers, inconclusive patch test readings (i.e., irritant reactions or weak positive reactions) were found in 17% with chlorhexidine acetate 1% aq., compared to 5% with chlorhexidine gluconate 1% aq., indicating a high degree of irritant potential of the acetate 1% aq. We consider that some positive reactions are lost if chlorhexidine gluconate 1% aq. only is used for patch testing, but that chlorhexidine acetate 1% aq., on the other hand, is an unacceptably strong irritant. We therefore suggest that further testing with chlorhexidine acetate 1 and 0.5% aq. should be performed, in parallel with chlorhexidine gluconate 1% aq., in order to establish appropriate test concentrations. We find that up to 13% of the leg ulcer patients in this study may be sensitized to chlorhexidine, and we recommend that the indications for the drug in leg ulcer patients should be reconsidered.

Dermatoses among floral shop workers

Concern about the increasing incidence of hand dermatitis in floral shop workers in the United States and its possible association to the plant Alstroemeria, a flower that has become popular since its introduction in 1981, prompted investigation of the prevalence and cause of hand dermatitis in a sample of floral workers. Fifty-seven floral workers were surveyed, and 15 (26%) reported hand dermatitis within the previous 12 months. Sixteen floral workers (eight with dermatitis) volunteered to be patch tested to the North American Contact Dermatitis Group Standard and Perfume Trays, a series of eight pesticides and 20 plant allergens. Of four of seven floral designers and arrangers who reported hand dermatitis, three reacted positively to patch tests to tuliposide A, the allergen in Alstroemeria. Patch test readings for all other plant extracts were negative. A positive reading for a test to one pesticide, difolatan (Captafol), was noted, the relevance of which is unknown.

Delayed patch test reactions at days 7 and 9

403 consecutive patients were examined on days 2, 4, 7, and 9 following application of patch tests. Late positive reactions, i.e., those which manifested after day 4, were seen in 29 patients (7.2%). The allergens which most commonly produced late positive reactions were neomycin (7), potassium dichromate (4), and cobalt (3). Paired patch test readings on days 4 and 7 were more reliable than those on days 2 and 4. If only 1 patch test reading were performed, a single reading on day 4 would have been most useful. The reading on day 9 proved to be of limited value. Of 11 patients who were retested after an interval of more than 6 months, 7 showed earlier eliciting reactions, which may have been due to active sensitization.

The case for patch test readings beyond day 2: Notes from the lost and found department

Additional patch test readings taken after 2 days (48 hours) are valuable in distinguishing false-positive reactions, which may occur up to 22% of the time. Second readings taken on days 3 through 7 may detect an additional 34% positive reactivity. Those reactions, both lost (initially positive, later negative) and found (initially negative, later positive) by delayed readings, require clinical correlation for relevance as do the readings that persist at and beyond day 2 (positive at both readings).

Quantification of cutaneous oedema in patch test reactions by measurement of skin thickness with high-frequency pulsed ultrasound.

69 doubtful and positive patch test readings (?+21, +23, ++18, 7) in 15 contact dermatitis patients were studied by measurement of skin thickness as an expression of allergic oedema. Exposed skin was compared with a regional control. Skin thickness was measured by 15 MHz pulsed ultrasound (A-scan) to 0.1 mm accuracy. The ?+, +, ++, and reactions could be separated by measurements of absolute difference in thickness (p less than 0.001, p less than 0.001, p less than 0.02) between exposed and non-exposed skin; the mean increases were 0.14, 0.49, 0.93, and 1.37 mm. The ?+, +, and ++ reactions, but not the reactions, could also be separated by measurements of relative increase in skin thickness (p less than 0.001, p less than 0.001, n.s.); the mean increases were 7%, 25%, 50% and 55%. The normal thickness of the skin of the back was shown to have increased (p less than 0.02) in patients with reactions only. It is concluded that the high-frequency ultrasound method is suitable for quantification of doubtful and positive patch test reactions. The reactions are probably explained by the normal thick skin of the back, and they need no separate recording in patch testing. Standards of increase in skin thickness in doubtful and positive patch tests are defined: absolute increase (mm) was ?+ less than or equal to 0.2; +0.3-0.7; ++0.8-1.3 ( greater than or equal to 1.4); relative increases were ?+ less than 15%; +15-45%, ++ ( included) greater than 45%.

Day 7 (D7) patch test reading - valuable or not?

Day 7 (D7) reading of 15,469 patch tests was carried out in 499 patients. In one fifth of them, positive reactions were observed at D7 having been judged negative at D2. The significance of the findings is discussed.