Spectrophotometric Measurement of Minimal Erythema Dose Sites after Narrowband Ultraviolet B Phototesting: Clinical Implication of Spetrophotometric Values in Phototherapy.
- Author:
Su Young JEON
1
;
Chae Young LEE
;
Ki Hoon SONG
;
Ki Ho KIM
Author Information
- Publication Type:Original Article
- Keywords: a*value; L*value; Skin phototype; Spectrophotometer
- MeSH: Erythema*; Humans; Phototherapy*; Pigmentation; Psoriasis; Skin; Skin Pigmentation; Tanning; Triacetoneamine-N-Oxyl; Vitiligo
- From:Annals of Dermatology 2014;26(1):17-25
- CountryRepublic of Korea
- Language:English
- Abstract: BACKGROUND: The spectrophotometer is well known to be a useful tool for estimating the objective minimal erythema dose (MED) during planning of phototherapy protocol. However, only a few spectrophotometric values are used to evaluate the erythema and pigmentation of the MED site during phototesting. OBJECTIVE: To determinea new meaning of the relationships among spectrophotometric values during phototesting. METHODS: Twenty-five patients with psoriasis and 23 patients with vitiligo were selected before undergoing narrowband ultraviolet B phototherapy. We interpreted the gross findings of erythema and measured the L*a*b* values using a spectrophotometer at each phototest spot. We compared MEDs, basic spectrophotometric values (L*a*b*), and b*/L* values separately according to skin type, and determined the correlation of each spectrophotometric value and the correlation between a* and b*/L* values. RESULTS: Among L*a*b* values, only b* values showed a statistically significant difference between the type III and IV groups (p=0.003). There was a positive correlation only between MEDs and b* values (p<0.05). The average b*/L*value in the type IV group was significantly higher than the type III group (p<0.05). CONCLUSION: The higher b* values in type IV skin indicates that skin tanning develops more prominently than type III. The correlation between MEDs and b* values may signify that the skin pigmentation status is deepened with the higher MEDs. The difference in b*/L*values between type III and IV skin reflects that the b*/L*value is thought to be an index of tanning. The a* value, known as an index of erythema, does not influence the degree of tanning.
