Comparison of Sensitivities of Skin Prick and Intradermal Tests with Oral Rechallenge Test: A Prospective Interventional Hospital-Based Study.

BACKGROUND: Identification of culprit drug causing adverse cutaneous drug reactions may not be possible clinically due to the intake of more than one drug. AIM: To compare the sensitivity of skin tests with gold standard oral rechallenge test to detect adverse cutaneous drug reactions.
MATERIALS AND METHODS: This is a prospective interventional hospital-based study of patients with adverse cutaneous drug reactions attending the outpatient department of dermatology and venereology at a tertiary care center over a 12-month period. Skin prick tests, intradermal tests, and oral rechallenge tests were performed in these patients and their sensitivities were compared. The data of quantitative nature is presented in mean and standard deviation, and categorical variables are presented in number and percentage. The sensitivity of skin tests is compared with the gold standard oral rechallenge test.
RESULTS: A total of 49 patients with adverse cutaneous drug reactions were evaluated. Clinical spectrum of adverse cutaneous drug reactions ranged from mild to severe, with fixed drug eruption being the commonest (55.1%) followed by maculopapular exanthem (32.7%). The highest incidence was with fluoroquinolones (43.8%) followed by nonsteroidal anti-inflammatory drugs. Fluoroquinolones were the major cause of fixed drug eruption followed by nonsteroidal anti-inflammatory drugs. The sensitivity of skin prick test and intradermal tests were 49% and 73%, respectively and the difference was highly significant (P < 0.001). The difference in sensitivity in skin prick test versus oral rechallenge test and intradermal test versus oral rechallenge test was also highly significant (P < 0.001). LIMITATIONS: Small sample size was a major limitation. Histopathological examinations and human leukocyte antigen associations could not be done.
CONCLUSION: Predominant causative drugs were fluoroquinolones followed by nonsteroidal anti-inflammatory drugs. Sensitivities of skin prick test and intradermal test were quite good and these skin tests should be performed before oral rechallenge test in cases of adverse cutaneous drug reactions. Copyright:

Introduction

Adverse cutaneous drug reactions (ACDRs) are major health problems causing considerable costs for health care systems.[1] They affect 2.2% of all hospitalized patients.[2] Most of the time patients take more than one drug, so it becomes difficult to identify culprit drugs. Skin tests or oral rechallenge test (ORT) can be an important tool in such cases. ORT is considered to be a gold standard test. It can sometimes be fatal in cases of severe ACDRs. So, skin tests may be tried in such situations. The present study was done to compare sensitivities of different skin tests to gold standard ORT.

Materials and Methods

The study design was a prospective interventional study conducted at a tertiary health care center of a teaching institute from August 2018 to July 2019. The study was approved by the institutional ethical committee and was registered with the clinical trials registry India (CTRI/2018/07/015023) (Date: 24/10/2017). All the patients with ACDRs except drug-induced hypersensitivity syndrome (DIHS), Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and SJS/TEN were included. The inclusion criteria were patients of age 13–65 years, both sexes, and those willing to give written informed consent. Pregnant and lactating females, children under 13 years, human immunodeficiency virus (HIV) infected patients, patients with uncontrolled asthma, patients with connective tissue diseases, renal disease, liver disease, and cardiac diseases, and those taking systemic steroids in last three weeks and antihistamines in last five days were excluded. Their demographic details were recorded. The provisional diagnosis of ACDR was made on the basis of history and clinical examination. Suspected drugs (taken during the last 12 weeks) were noted down. They were called for testing after two weeks of resolution of ACDR. Three tests (skin prick test, intradermal test, and oral rechallenge test) were performed one week apart in each patient. Skin prick test and intradermal tests were performed on the volar aspect of the forearm with the commercially available injectable solution form or a solution made by crushing tablets in normal saline 0.9%. In SPT, one drop of suspected drug solution of each drug was placed on the volar forearm skin and percutaneous prick was made by separate 26 G needles at 20° angle and 2 mm deep. Histamine chloride solution (10 mg/mL) was used to perform positive control and 0.9% normal saline for negative control. Reading was taken after 20 minutes. The test was considered positive if a wheel of a diameter greater than three mm than that of the negative control was present. If the result was negative, a delayed reading was taken after 24 hours.[34]

For the intradermal test, a sterile solution of the suspected drug was taken and sequentially diluted to 10-1 and 10-2 concentrations. Solution (0.05 mL) was injected intradermally, which produced a bleb. Positive and negative controls were the same as SPT. The first IDT was performed with a 10-2 dilution. Reading was taken after 30 minutes. If the result was negative, then subsequent IDTs were performed with higher serial dilutions up to the standard dilution, with 30 minutes intervals, until the results came out to be positive. The test was considered positive if a wheel of greater than ten mm diameter developed. Delayed readings were performed at 6 hours and one day. If the IDT results were negative, a phone call was made to the patient after one week to confirm if the results remained negative or not, or a delayed reading at one week was performed.[34]

ORT was performed one week after the IDT. It was started with one half of a single therapeutic dose, followed if necessary, by a step-wise increase to full dose.[5] A positive test was indicated if any of the following occurred: erythema at or around the existing lesion, generalised itching, anasarca, development of new lesions, or generalized erythema. ORT was considered negative if the above symptoms were not seen within 24 hours.

The data of quantitative nature was presented in mean and standard deviation, and categorical variables were presented in number and percentage. The sensitivity of skin prick test and intradermal test were compared with the gold standard oral rechallenge test. Chi square test was used to compare the sensitivities between the tests.

Results

A total of 55 patients of ACDR were enrolled but only 49 patients were included in the study. Six patients were excluded from the study in which three lost to follow-up after SPT and three lost after IDT.

The most prevalent type of reaction was fixed drug eruption (55.1%) mainly caused by fluoroquinolones, followed by maculopapular exanthem (32.7%) in which culprit drugs were nonsteroidal anti-inflammatory drugs (NSAIDs). The most common group of drugs responsible for ACDRs were fluoroquinolones (43.8%) followed by nonsteroidal anti-inflammatory drugs [Table 1].

Table 1

Distribution of drugs according to the common types of ACDR

Drugs	FDE (n=27, 55.1%)	MPE (n=16, 32.7%)
Antibiotics
Norflox	25%	7.1%
Oflox	21.4%
Cipro	10.7%
Doxy	3.57%	7.1%
TMP-SMX		7.1%
Cefpo
NSAIDs
Para	10.7%	28.6%
Diclo	10.7%	7.1%
Nim	3.57%	7.1%
Antiepileptic drugs
Valpro		7.1%
Levetira		7.1%
Pyrazinamide		7.1%
Nitroimidazoles
Tini	7.1%
Secni	3.57%
Orni	3.57%

Abbreviations: FDE- fixed drug eruption, MPE- maculopapular exanthem, AE- angioedema, AGEP-acute generalized exanthematous pustulosis, SDRIFE- symmetrical drug-related intertriginous and flexural exanthem, Norflox- norfloxacin, oflox- ofloxacin, cipro- ciprofloxacin, amoxi- amoxicillin, doxy- doxycycline, TMP-SMX- trimethoprim-sulphamethoxazole, cefpo- cefpodoxime, para- paracetamol, diclo- diclofenac, nim- nimesulide, valpro- valproate, levetira- levetiracetam, itra- itraconazole, tini- tinidazole, secni- secnidazole, orni- ornidazole.

The sensitivity of the skin prick test was 49%. The most common class of drug showing skin prick test positivity was fluoroquinolones (28.5%) mainly norfloxacin and ciprofloxacin (8.2% each) followed by NSAIDs (16.3%) mainly paracetamol (8.2%). The sensitivity of the intradermal test was 73.5%. The most common class of drugs showing IDT positivity was fluoroquinolones (38.8%) mainly norfloxacin and ofloxacin (14.3% each) followed by NSAIDs (24.4%) mainly paracetamol (10.2%) [Table 2].

Table 2

Positivity of skin tests compared with ORT

Type of ACDR	Sensitivity
	SPT 24 (49%)	IDT 36 (73.5%)	ORT 49 (100%)
FDE	13 (26.53%)	21 (42.85%)	27 (55.10%)
MPE	9 (18.37%)	11 (22.45%)	16 (32.65%)
Urticaria and/AE	1 (2.04%)	1 (2.04%)	2 (4.08%)
SDRIFE	1 (2.04%)	1 (2.04%)	1 (2.04%)
AGEP	0	0	(2.04%)
Oral ulcers	0	1 (2.04%)	1 (2.04%)
Erythroderma	0	1 (2.04%)	1 (2.04%)
	Positive SPT	Positive IDT	Positive ORT
Age (in years)
13-20	9 (37.5%)	10 (27.8%)	15 (30.6%)
21-30	7 (29.2%)	15 (41.7%)	18 (36.7%)
31-40	2 (8.3%)	3 (8.3%)	6 (12.2%)
41-50	4 (16.7%)	6 (16.7%)	6 (12.2%)
>50	2 (8.3%)	2 (5.6%)	4 (8.3%)
Male	16 (66.7%)	25 (69.4%)	32 (65.3%)
Female	8 (33.3%)	11 (30.6%)	17 (34.7%)
Norfloxacin	4 (8.2%)	7 (14.3%)	8 (16.7%)
Paracetamol	4 (8.2%)	5 (10.2%)	8 (16.7%)
Ofloxacin	3 (6.1%)	7 (14.3%)	8 (16.7%)
Diclofenac	2 (4.1%)	3 (6.1%)	5 (10.4%)
Ciprofloxacin	4 (8.2%)	5 (10.2%)	5 (10.4%)
Ibuprofen	1 (2%)	3 (6.1%)	2 (4.2%)
Tinidazole	1 (2%)	1 (2%)	2 (4.2%)
Nimesulide	1 (2%)	1 (2%)	2 (4.2%)
Itraconazole	1 (2%)	1 (2%)	2 (4.2%)
Secnidazole	0	0	1 (2.1%)
Cefpodoxime	1 (2%)	1 (2%)	1 (2.1%)
Pyrazinamide	0	1 (2%)	1 (2.1%)
Valproate	1 (2%)	1 (2%)	1 (2.1%)
Levetiracetam	0	0	1 (2.1%)
Amoxicillin	0	1 (2%)	1 (2.1%)
Doxycycline	1 (2%)	1 (2%)	1 (2.1%)
Sulpha drugs	0	1 (2%)	1 (2.1%)
Ornidazole	0	0	1 (2.1%)

ACDR- adverse cutaneous drug reaction, SPT- skin prick test, IDT- intradermal test, ORT- oral rechallenge test, FDE- fixed drug eruption, MPE- maculopapular exanthem, AE- angioedema, AGEP-acute generalized exanthematous pustulosis, SDRIFE- symmetrical drug-related intertriginous and flexural exanthema

The sensitivity of IDT was found to be more than SPT, which was highly significant (P < 0.001). The sensitivity of both the skin tests was less than ORT, and this difference was highly significant (P < 0.001) [Table 2]. The most common age group showing SPT and IDT positivity was 13–20 years (37.5% and 27.8%, respectively). They were more common in males (66.7% and 69.4%) than females (33.3% and 30.6%). Maximum SPT and IDT were positive in fixed drug eruption (FDE) cases (54.1% and 58.3%, respectively) followed by maculopapular exanthem (MPE) (29.2% and 25%).

Discussion

ACDRs are one of the common causes of morbidity and mortality. They can arise due to immunologic or nonimmunologic mechanisms.

There are various tests to find out the culprit drugs, such as skin tests (patch test, skin prick test, and intradermal test), radioallergosorbent test (RAST), lymphocyte transformation test (LTT), and oral rechallenge test. The sensitivity of the patch test is 43%,[3] that of RAST ranges from 42.9% to 75%[6], and LTT is 78%.[7] They have technical limitations, cost constraints, and low sensitivity. So, with the discovery of more feasible and quick methods, which can be performed by clinicians in outpatient departments, there is a huge scope for skin prick tests and intradermal tests.

The patch test is used for delayed hypersensitivity, prick test for immediate and intradermal for both immediate and delayed hypersensitivity. We have chosen only two tests among skin tests because in patch test additional readings are taken after 2 and 4 days, sometimes, after 7 days, for which patient has to be hospitalized also. Patch tests carried out on previously uninvolved skin are rarely positive if the reaction is fixed drug eruption and most of our patients were of FDE.

In this study, 21–30 years was the most common age group (36.7%), which is in accordance with previous studies.[8910]

There is a predominance of males in our study (65.3%) as compared to females (34.7%), which is comparable to other studies.[811] However, in some studies either females were more affected[12] or both were equally affected.[13]

FDE was the most common type of ACDR (55.1%) followed by MPE (32.7%) as in other studies.[91415] This was in contrast to other studies.[161718192021]

Antibiotics were the most common drugs implicated in our study, mainly fluoroquinolones (43.8%). Our results were comparable to various other studies.[91314162223]

In the present study, the maximum number of patients had onset of ACDR within 3–15 days (36.7%), which is comparable to other studies.[916]

The majority of the patients in our study who had ACDR within 24 hours, were of FDE. The onset of MPE was within 3–15 days. The results of Noel et al.[20] and Choon et al.[24] were also comparable to our study. Our results were in contrast to some studies.[82526]

In our study, the sensitivity of SPT was 49%. Till now, different sensitivity patterns of SPT were noted, which ranged from 1.1%[27] to 71%.[28] In a study performed by Perez et al. in patients with quinolone allergy, 20% of cases had a positive SPT.[29] In most of the studies, SPT and IDT were done separately while in our study as well as in a few other studies, both tests were done in the same patients.[329]

The sensitivity of the intradermal test shows quite a similar trend over the last 18 years, which continues in the present study.[327] Regarding IDT, 80% of quinolone allergic subjects have been reported to give positive test results, although the possibility of an irritant response was not ruled out.[27] Perez et al. showed a sensitivity of IDT to be 75%.[29]

The sensitivity of IDT was more than SPT in our study, which was highly significant (P < 0.001). Sensitivities of both SPT and IDT were less than ORT, and this difference was highly significant (P < 0.001). In spite of less sensitivity in comparison to ORT, the skin tests have got quite good sensitivity. These findings suggest first to perform skin tests and if negative and clinically highly suspected, then go for oral rechallenge test.

Limitations of this study: In vitro tests like radioallergosorbent test (RAST), lymphocyte transformation test (LTT), human leukocyte antigen (HLA) association, and basophil activation tests were not carried out due to resource and cost constraints. Our sample size was small. Histopathology could not be done for the diagnosis of ACDR.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.