|MUSINGS/OPINIONS/TIPS AND EXPERIENCES
|Year : 2012 | Volume
| Issue : 1 | Page : 57-58
Transporting preloaded chambers for patch testing
Srinivas R Chakravarthi
Department of Dermatology and STD, PSG Hospitals, Coimbatore, Tamil Nadu, India
|Date of Web Publication||3-Mar-2012|
Srinivas R Chakravarthi
Department of Dermatology and STD, PSG Hospitals, Coimbatore - 641 004, Tamil Nadu
|How to cite this article:|
Chakravarthi SR. Transporting preloaded chambers for patch testing. Indian Dermatol Online J 2012;3:57-8
Patch testing is a useful test to detect allergy. It is simple, reliable, and easy to perform. The patch test technique and its interpretation have been standardized by International Contact Dermatitis Research Group. Various batteries are available for patch testing and these include the most commonly used Standard series and various specific series such as Dental series, Scandinavian Photopatch series, Footwear series, and so on. It is advisable that centers dedicated to patch testing stock various antigens based on need. Even these centers may find it difficult to stock all the series, which is an expensive proposition. Each series costs Rs 11,000 to 40,000 has a shelf life of about 2 years and occupies space in the refrigerator.
It would be helpful if each center stocks select antigens based on demand and need and any patient who needs to be tested with the series can be sent to that particular center. It would be inconvenient for patients to travel to the center for testing and subsequent readings so readings can be taken by the referring center if it has the expertise.
I run a clinic at the city center and regularly test patients with Indian Standard Series. A lady recently presented with ulceration and lichenification of the buccal mucosa which corresponded to the site where amalgam filling had been performed 5 years ago. Sensitivity to amalgam was suspected and I decided to test her with Dental series which was available to me at the institution but not in the clinic.
Patient was requested to report after few days for patch testing at the clinic. The Finn chamber was charged by standard method in the institution with Dental series obtained from Chemotechnique AB, Sweden, as follows. A standard tape with Finn chambers glued to it was placed on a table and partly removed from the non-adhesive paper and placed on a green cloth. Another set of chambers was removed from the adhesive tape with a forceps and placed on the same cloth beside the mother chamber. The first set of chambers was charged with antigens from the Dental series [Figure 1]. Using forceps the loose chambers were placed individually over the charged chambers and gently pressed [Figure 2]. The chambers were placed in such a manner that the hollow of the chamber faced each other and the rim opposed each other. The chambers were glued to each other because the white petrolatum vehicle of the antigens provided the required tackiness.
The original non-sticky sheet was replaced over the loaded chambers and gently pressed to ensure that the tape was properly stuck [Figure 3].
The four strips of loaded chambers were wrapped in a polythene paper and taken to the clinic and placed in the refrigerator. They can also be placed between two sheets of cardboard before transporting to prevent crushing. The patient reported after 3 days. The hypoallegenic micropore tape was separated from the non-adhesive supporting sheet, and the chambers covering the mother chambers were individually removed. Any antigen adhering to the chamber used for covering was replaced into the mother chamber with the forceps. Although there is a possibility of loss of minute amount of antigen during separation of opposing chambers, we do not think this will make difference because delayed allergy elicited by patch testing can be elicited by very small amount of antigens. Care was, however, taken to prevent contamination of the antigens.
The loaded chambers were used for patch testing and the duplicate chambers were discarded. Positive reaction was elicited by potassium dichromate, mercury, gold sodium thiosulfate, and nickel sulfate [Figure 4].
Dental series, however, does not have liquid antigens so we have no experience of transporting liquid antigens. If an absorbing material or paper with a slightly smaller than the diameter is placed on the chamber, soaked with liquid antigen and then covered with the opposing chamber, one may be able to transport liquid antigens too.
I feel that this simple way will enable a dermatologist to patch test with almost any series without having to invest a large amount of money in procuring the entire series. The preloaded chambers can be sent by courier from one center to another. Although we prefer to refrigerate the antigens to prolong its shelf life, we do not think the results will get altered but this calls for a separate study that we may undertake in future. At present we are unable to comment on how long antigens can be kept out of the refrigerator without affecting the readings.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]