Simple objective measurement of the cutaneous delayed-type hypersensitivity reaction to tuberculin using spectrophotometry.
OBJECTIVE
A number of subjective methods have been used to quantify the extent of the cutaneous delayed-type hypersensitivity (DTH) reaction. However, because of their subjective nature, significant differences in measurements may be seen between individual observers or laboratories unless thorough training is given to each observer.


METHODS
Objective measurement of the DTH reaction using a hand-held spectrophotometer is described. Guinea pigs were primed using inoculation with Mycobacterium bovis Bacille Calmette-Guerin and challenged five weeks later in the shaved flank with three doses of bovine purified protein derivative. The extent of the ensuing DTH reaction was measured 24 and 48 h later. Spectrophotometric measurement of the reaction site was compared with a control region of skin on each animal and expressed as the change within a standard colour space. Data obtained with the spectrophotometer was compared with the subjective measurement of the area of the DTH reaction by an experienced operator.


RESULTS
The measurements obtained with the spectrophotometer correlated very closely with conventional measurement of the reaction area by a trained operator. The reaction size in square mm and changes along the red/green colour axis was correlated most strongly.


CONCLUSIONS
Spectrophotometric measurement of the DTH reaction had advantages over conventional measuring techniques in terms of speed, reproducibility and reduced operator to operator variation. We conclude that the cutaneous DTH reaction may be simply and objectively quantified with the use of a hand-held spectrophotometer.
Chambers
Mark A
MA
TB Research Group, Department of Bacterial Diseases, Veterinary Laboratories Agency, Addlestone, Surrey, UK.
Jahans
Keith
K
Whelan
Adam
A
Hughes
Catherine
C
Sayers
Robin
R
Perkins
Alan
A
Glyn Hewinson
R
R
D000818:Animals; D003124:Colorimetry / Q000379:methods*; D017449:Dermatitis, Allergic Contact / Q000145:classification / Q000175:diagnosis / Q000209:etiology; D004342:Drug Hypersensitivity / Q000145:classification / Q000175:diagnosis* / Q000209:etiology; D006168:Guinea Pigs; D006968:Hypersensitivity, Delayed / Q000139:chemically induced / Q000145:classification / Q000175:diagnosis*; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012867:Skin / Q000276:immunology / Q000503:physiopathology; D013053:Spectrophotometry / Q000379:methods*; D014373:Tuberculin
D014373:Tuberculin