An audit to identify the optimum referral rate to a contactdermatitis investigation unit

M.BHUSHAN AND M.H.BECK

Contact Dermatitis Investigation Unit, Department of Dermatology, Hope Hospital, Salford M6 8HD, U.K.

Accepted for publication 11 March 1999

Summary The principle of patch testing is to identify individuals with a contact allergy of relevance to their

disorder and to provide avoidance advice in an attempt to improve or resolve their condition. We

aimed to de®ne an optimum referral rate to a centralized contact dermatitis unit using a retrospectiveanalysis of data relating to 10 consultants. The results showed no signi®cant difference (P�0´21) in

the percentage of relevant positive individuals identi®ed between the consultants. However, a linear

relationship (r�0´99) was seen between the number of relevant positive allergic reactions and thenumber referred by individual consultants. We propose that the minimal annual referral rate for

patch testing from a predominately urban population in a developed country is one in 700 of the

population.

Key words: audit, contact dermatitis, referral rate.

Eczema is the most common reason for a new referral toa dermatology department in the U.K.1 In common with

other medical disorders, assessment requires a careful

history, examination and appropriate investigations.Patch testing, at present the only practical scienti®c

procedure for the diagnosis of allergic contact dermati-

tis, must be performed in eczematous disorders if unsus-pected relevant contact allergens are to be identi®ed.2

Manchester is unusual in possessing a centralized

contact dermatitis unit to which all consultant derma-tologists refer their patients. We were aware that the

numbers referred from each consultant varied signi®-

cantly, with individuals clearly possessing differentthresholds for sending patients to the contact dermatitis

unit. There was therefore an opportunity to audit each

consultant's referral pattern retrospectively.

Materials and methods

We aimed to identify an optimum referral rate by

examining, over a period of 17 months: (i) the total

number of individuals referred to the unit, and (ii) theproportion of those with one or more positive patch tests

of present relevance to their disorder, for each consul-

tant, anonymously. At the time of the audit, each of the

consultants had very similar catchment numbers andclinical workloads and patch testing was undertaken

entirely at the contact dermatitis investigation unit.

The patch tests were read and interpreted by derma-tologists experienced in the ®eld of contact dermatitis

and under the supervision of a single consultant in

charge of the unit, to maintain consistency in thereadings and interpretation of positive results. A rele-

vant patch test was de®ned as a positive allergic reaction

at 48 and 96 h to a substance to which the patient hadbeen exposed and which was felt to be an initiating and/

or exacerbating factor in their eczema. In addition to the

positive results, clinical and demographic details,derived from both the clinical notes and interview

with the patient at the time of patch testing, were

documented on a standard proforma and subsequentlyentered into a database. Details relevant to the study

were collected from this. Statistical analysis was per-

formed using the x2-test and Pearson's correlationcoef®cient analysis.

Results

During the study period of 17 months, the range of

referrals to the contact dermatitis unit varied from 77 to522 (mean 196) for each of 10 consultants. The

percentages for relevant positive allergic reactions

were very similar. There were no statistically signi®cant

British Journal of Dermatology 1999; 141: 570±572.

570 q 1999 British Association of Dermatologists

Correspondence: M.Bhushan.

E-mail: mbhushan@fs1.ho.man.ac.uk

differences in the proportion of referrals found to have

one or more relevant positive allergic reactions betweenconsultants (P�0´21: data not shown). There was a

very clear linear relationship (r�0´99, P�0´001)

between the number of individuals with relevant aller-gic contact dermatitis and the number referred by each

consultant (Fig. 1). The demographic data are shown in

Table 1.

Discussion

Calnan once stated that `the greatest abuse of patchtesting is failure to use it'.3 The principle of patch testing

is to identify individuals with a contact allergy of

relevance to their disorder, with a view to providingavoidance advice and improving or clearing their con-

dition.4 A study by Lewis et al.5 con®rms the bene®cial

effects of patch testing from a patient's perspective. If

patch testing is not performed and relevant contactallergies are not identi®ed, individuals may be at risk

of a recalcitrant dermatitis which responds poorly and

incompletely to therapy. Inevitably, this will be re¯ectedin increased morbidity and ®nancial disadvantage to the

patient,6,7 in addition to time and revenue conse-

quences for the health service.8 At the same time, it isof importance to the clinician (and manager) that

resources concerned with investigation of these pro-

blems are used ef®ciently and in a cost-effective manner.The aim of the audit was to investigate whether we

could identify a set of criteria which would enable us to

prevent excessive referral numbers to the contact der-matitis investigation unit while not overlooking large

numbers of individuals with relevant positive patch test

results. It was also hoped that we could identify a cohortof consultants whose referral practice re¯ected such

criteria.

When we analysed each consultant's percentage ofrelevant positive individuals, it became apparent that

there was no signi®cant difference between them. Our

®nding of an average positive relevant allergy detectionrate of 46% (data not shown) is in keeping with con-

clusions reached by Rietschel,9 who felt the appropriate

use of patch testing should yield a positive (and oneassumes relevant) result 30±65% of the time. However,

we have reached a further important conclusion. It isclear that despite each consultant covering a similar

clinical load, catchment population and demographic

distribution of districts central and peripheral to the city,those who referred the greatest numbers also identi®ed

the most individuals with a relevant contact allergy.

Furthermore, the relationship was linear. If consultantswere referring excessive numbers of patients, i.e. if they

were unselective in their referral patterns, then a

plateau effect would occur in Figure 1; i.e. a lower

REFERRAL TO A CONTACT DERMATITIS UNIT 571

q 1999 British Association of Dermatologists, British Journal of Dermatology, 141, 570±572

Figure 1. A linear relationship is seen between numbers of individuals

referred by consultants and numbers identi®ed to have a relevantpositive allergic reaction (P�0´001, r�0´99).

Table 1. Demographic data for patients referred by consultants 1±10 to the contact dermatitis investigation unit

Consultant No. of males No. of females No. of occupational cases No. of hand cases No. of leg/stasis cases Total no. of cases

1 35 42 16 36 3 77

2 47 71 16 65 0 118

3 53 72 13 61 4 125

4 62 66 20 59 1 1285 49 83 11 57 3 132

6 52 106 16 58 1 158

7 56 109 11 60 4 1658 92 177 14 101 8 269

9 88 184 19 105 25 272

10 202 320 49 190 18 522

percentage of relevant positive allergic reactions wouldbe seen. We conclude from our data that consultant 10

refers the minimum number per annum appropriate for

the catchment population which he/she serves (equiva-lent to 260,000).

It is necessary to consider whether certain consul-

tants were more likely to receive referrals from generalpractitioners than others, perhaps because they were

considered to have a specialist interest in the ®eld of

contact dermatitis. This does not appear to be the case,as all consultants involved in this study felt strongly that

their general practitioner referrals were unselective.

Additionally, many catchment areas are covered by asingle consultant and he/she would receive the vast

majority of all dermatological cases.

As a result of this study, we calculated that theannual referral rate of consultant 10 was one per 700

(1416 per million) of catchment population. We suggest

that this is the minimum appropriate referral rate for apredominately urban population in a developed coun-

try, and suspect that such a rate is rarely achieved

world-wide. In addition, we must bear in mind thatone per 700 is the absolute minimum ®gure for several

reasons. We do not know whether the threshold of

consultant 10 is still too low. Secondly, family practi-tioners almost certainly do not refer every patient who

would bene®t from patch testing to a consultant derma-tologist. Finally, not all patients appropriate for patch

testing will be prepared to travel to the contact derma-

titis unit for assessment and reading of the patches onthree separate occasions within a working week.

In light of the ®ndings from this study, consultant 10

was approached and asked for his/her criteria forreferral of patients for patch testing. These included:

(i) eczematous disorders where a contact allergy is

suspected or is failing to respond to treatment asexpected, especially if affected sites include the face,

eye, ear and perineum; (ii) chronic hand and footeczema; and (iii) varicose eczema. It is the conclusion

of this audit that these categories be regarded as appro-

priate indications for referral for patch testing in ourpopulation.

In addition to identifying clear guidelines for referral

for patch testing, we feel this audit has given someindication of the resources necessary to ensure ade-

quate provision of services for a contact dermatitis

investigation unit. We hope our ®ndings will be helpfulto those involved in cases of contact dermatitis who

wish to achieve an adequate and appropriate service for

their patient populations.

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