A positive cobalt spot test falsely indicating an occupational allergic contact dermatitis caused by cobalt.
BACKGROUND
For investigation of chemical exposure in allergic individuals, spot tests are invaluable. A reagent may react with a specific compound to give a specific typical colour, and thus indicate the presence of the specific substance. Spot tests can give both false-negative and false-positive reactions. To confirm the presence of the substance and quantify it, more sophisticated methods are required. On the basis of a positive cobalt spot test result, a woman was initially diagnosed with an occupational allergic contact dermatitis caused by cobalt.


OBJECTIVE
To investigate cobalt release from three different metal weaves to which our patient was occupationally exposed.


METHODS
The cobalt gel test and atomic absorption spectroscopy (AAS) were used to investigate the metal weaves. Two types of extract based on artificial sweat and nitric acid, respectively, were investigated with AAS.


RESULTS
No cobalt release was demonstrated with AAS.


CONCLUSIONS
When a diagnosis of allergic contact dermatitis caused by a sensitizer based on a positive spot test result will have far-reaching consequences, such as change of work, retraining, and claim on and payment of worker's compensation, conformational analysis must be performed.
Department of Occupational and Enviromental Dermatology, Skåne University Hospital, Lund University, Malmö, S-205 02, Sweden. magnus.bruze@med.lu.se
Magnus
M
Bruze
Haneen
H
Hamada
Jakob
J
Dahlin
Kari
K
Dunér
Lena
L
Persson
D000497:Alloys / Q000032:analysis / Q000737:chemistry; D003035:Cobalt / Q000032:analysis / Q000276:immunology*; D017449:Dermatitis, Allergic Contact / Q000209:etiology* / Q000276:immunology*; D009783:Dermatitis, Occupational / Q000209:etiology* / Q000276:immunology*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects*; D013054:Spectrophotometry, Atomic
D000497:Alloys; D003035:Cobalt
AAS; alloys; cobalt; contact allergy; false positive