Comparison of Dermoscopy and Wood’s Lamp in the Assessment of Stability of Vitiligo

Abstract

Background:

The stability of vitiligo is mainly assessed using clinical criteria. Wood’s lamp and dermoscopy have been proposed as valuable alternatives.

Objective:

The objective of the study was to compare the utility of dermoscopy and Wood’s lamp examination in the assessment of stability in vitiligo compared with clinical criteria and to define the best cutoff score using BPLeFoSK criteria in determining vitiligo stability.

Patients and Methods:

The study was conducted among patients with vitiligo attending a tertiary care center. The study design was a diagnostic test evaluation. One hundred and ten patients with vitiligo were recruited over 18 months. The most recent lesion in each patient was assessed for its stability using the clinical evaluation, Vitiligo Disease Activity (VIDA) score, Wood’s lamp, and dermoscopy with the BPLeFoSK score, where a score ≥1.5 indicated stable vitiligo.

Results:

The study revealed moderate agreement between Wood’s lamp and dermoscopy (κ=0.55) and a fair agreement between clinical evaluation and both Wood’s lamp (κ=0.33) and dermoscopy (κ=0.40). Wood’s lamp showed 72.3% sensitivity and 66.7% specificity, while dermoscopy had 74.1% sensitivity and 73.5% specificity. Wood’s lamp had 87% accuracy in identifying stable vitiligo but only 43.9% accuracy in ruling it out compared to clinical criteria. Dermoscopy demonstrated slightly higher effectiveness. The area under the receiver operating characteristic curve for dermoscopy versus clinical criteria was 0.826, while Wood’s lamp scored 0.695. A BPLeFoSK cutoff score of ≥3.5 was specific (97.6%) for identifying stable vitiligo, but sensitivity was low (25.6%).

Limitations:

The study’s limitations included the cross-sectional study design, examination of only one lesion per patient, lack of blinding, absence of follow-up, absence of histopathologic examination of the lesions, lack of sequential observation through a combination of clinical, dermoscopic, or Wood’s lamp examination, and utilization of VIDA scoring system which itself has recall bias. Use of a non-validated scoring system (BPLeFoSK) is also a limitation of this study.

Conclusion:

This study shows that dermoscopy and Wood’s lamp are equally helpful in clinical assessment. We propose a cutoff score of more than or equal to 3.5 in BPLeFoSK score.

Introduction

Vitiligo is a chronic disease that can be stable or progressive. This differentiation is essential for choosing the right treatment modality for a given patient. In cases where surgery is considered, ascertaining stability is important because surgical interventions can be attempted only in stable cases. Similarly, medical management also differs in stable and unstable cases. A patient with no new lesions and who lacks progression of the existing lesions for 2 years, absence of recent Koebner phenomenon, positive mini graft testing, absence of Koebner phenomenon at the donor site, and evidence of repigmentation of existing patches either spontaneously or with medical therapy is generally considered to have stable vitiligo.[1] However, there is no consensus regarding the minimum period of stability. It ranges from 4 months to 3 years in different studies.[2,3,4,5,6,7] Indian Association of Dermatologists, Venereologists, and Leprologists (IADVL) dermatosurgery task force defines a stable case of vitiligo as follows: if the patient reports no new lesions, there is no progression of existing lesions, and no Koebner phenomenon during the past 1 year.[8] Though recommended, performing mini-graft testing in all vitiligo patients is cumbersome and may not be feasible.[4] Histopathology is an invasive technique and is not routinely done as that itself can lead to the Koebner phenomenon.[9] Currently, most dermatosurgeons assess stability using clinical criteria.[8] But clinical criteria depend on the history and are prone to recall bias. So, in recent years, various objective methods like dermoscopy and Wood’s lamp have been evaluated to objectively determine the stability.[10]

There are previous studies assessing the usefulness of Wood’s lamp in assessing the stability of vitiligo.[11,12,13]Benzekri and Gauthier[11] reported that under Wood’s lamp illumination, stable vitiligo had well-defined borders, whereas active lesions appeared hypomelanotic with ill-defined borders. Wang et al.[12] used Wood’s lamp to assess stability, the timing of surgical grafting, and early recognition of pigmentation postoperatively. There are previous studies evaluating the role of dermoscopy in assessing stability in vitiligo.[14,15,16,17]

However, studies comparing the utility of Wood’s lamp versus dermoscopy in assessing disease stability are sparse.[14]

Patients and Methods

This study was conducted in the dermatology outpatient clinic of a tertiary care center. We included all patients with a definite clinical diagnosis of vitiligo, irrespective of type, diagnosed by a dermatologist. We excluded patients who did not give consent for participation. The sample size was calculated as per the formula:

where Z _1-α/2 is 1.96;

‘P’ is the specificity substituted as 94.4% based on the previous study by Nirmal et al.[14]

‘d’ is the relative precision set as 5% of specificity.

Though the calculated sample size was 91, all the eligible patients who attended the clinic during the study period of 18 months were included in the study.

The study was approved by the institutional ethics committee (B6-155/2019/MCTCR (22)). A written informed consent was obtained from all study participants. In case of patients younger than 18 years, the consent was obtained from their parents. Demographic details and the duration of the disease were recorded in a proforma. The most recent lesion was chosen in each patient for evaluation. Clinical examination was done to assess the type, anatomical distribution, and presence of the Koebner phenomenon. Disease activity was measured using the Vitiligo Disease Activity score (VIDA score).[18] Clinical criteria were considered the gold standard.

After the clinical evaluation, Wood’s lamp illumination test was performed on the selected lesion to assess stability. On Wood’s lamp illumination, stable vitiligo appears amelanotic with sharply defined borders. Unstable vitiligo appears hypochromic with ill-defined borders.[11] The same lesion was subjected to dermoscopic evaluation. The dermoscope (dermlite DL3N) attached to a mobile camera was used to record the dermoscopic pictures. The parameters assessed were scored using the BPLeFoSK system, which represents border, pigment network, perilesional hyperpigmentation, perifollicular pigmentation, satellite lesions, and micro-Koebner phenomenon, and the cumulative score was calculated. A cutoff score ≥1.5 was considered stable vitiligo.[14]

Definition of study variables

• Stable vitiligo was clinically defined as presenting with no new lesion, no extension of the pre-existing lesion, and no Koebner phenomenon for the past 1 year.[8]

• A lesion which failed to meet the above mentioned criteria was considered unstable vitiligo.

• VIDA scores of 0 and -1 were considered as stable vitiligo.

• VIDA scores of +4, +3, +2, and +1 were considered as active disease.

• On Wood’s lamp examination, stable vitiligo appears amelanotic with sharply defined borders.[11]

• Dermoscopic findings in stable vitiligo are

  1. Well-defined borders

  2. Absent or reticulate pigment network

  3. Perilesional hyperpigmentation

  4. Perifollicular pigmentation

  5. Absent satellite lesions

  6. Absence of micro-Koebner phenomenon.

Each of the parameters was given a score using the BPLeFoSK system. A cumulative score of ≥1.5 was defined as stable vitiligo.[14]

The features of unstable vitiligo are

1. Ill-defined borders

2. Reverse/reduced pigment network

3. Absence of perilesional pigmentation

4. Perifollicular depigmentation

5. Satellite lesions

6. Micro-Koebner phenomenon.

A cumulative score of <1.5 was considered unstable vitiligo.

Statistical analysis

Statistical analysis was done using SPSS software version 25 (IBM Corporation, Armonk, New York, USA). From the collected demographic and clinical information, all qualitative data were expressed as percentages, and all quantitative data were expressed as mean and standard deviation. The utility of dermoscopy and Wood’s lamp to assess the activity in vitiligo was evaluated by calculating the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The agreement between the three diagnostic methods was ascertained by kappa analysis and was graded using the Landis and Koch scale.[19] The receiver operator characteristic (ROC) curve was plotted, and the area under the ROC curve was assessed at different levels of BPLeFoSK score.

Results

We studied one representative lesion each from 110 individuals with vitiligo.

Baseline characteristics

The youngest participant in the study was 3 years old, and the eldest was 80 years old. Twenty-seven (24.5%) patients were of the age group 0–14 years. Out of 110 patients, 58 study participants (52.7%) were females, and 52 were males (47.3%). The male–to–female ratio was 1:1.12.

Duration of the disease

The disease duration was less than 1 year in 24 (21.7%) of the study participants. The majority of the study participants (n = 41; 37.2%) had a disease duration of 1–5 years.

Type of vitiligo

The majority of study subjects (n = 66; 60%) had a generalized disease, and 44 (40%) had a localized disease. Among the localized types of vitiligo, the most common type was focal vitiligo (n = 35;28.18%). The least common type noted was mucosal vitiligo (n = 5;4.54%); 7.2% of patients had segmental vitiligo, and 28.18% had focal vitiligo.

Vitiligo disease activity scoring (VIDA scoring)

The activity of vitiligo was assessed using the VIDA score. Twenty-seven (24.5%) patients had a stable disease. Four (3.6%) of the study participants had spontaneous repigmentation of the patches. Thirty-eight participants (34.54%) had disease activity of <6 weeks [Table 1]. The majority (83, 75.45%) of the study participants had unstable vitiligo.

Table 1.

Vitiligo Disease Activity (VIDA) score among the study participants

VIDA score	Number of participants (%)
+4 (activity of < 6 weeks)	38 (34.54%)
+3 (activity of 6 weeks to 3 months)	16 (14.54%)
+2 (activity of 3 months to 6 months)	21 (19.09%)
+1 (activity of 6 months to 12 months)	8 (7.2%)
0 (stable for 1 year or more)	23 (20.90%)
-1 (stable with spontaneous repigmentation since 1 year or more)	4 (3.6%)

Wood’s lamp examination

Forty-one (37.3%) individuals showed achromic and well-defined borders, which are the features of stable vitiligo [Figure 1a], and 69 (62.7%) showed hypochromic and ill-defined borders, suggestive of unstable vitiligo [Figure 2a].

Figure 1.

(a) Wood’s lamp examination of a case of stable vitiligo demonstrating well-defined borders. (b) Polarized dermoscopy (x10) of stable vitiligo demonstrating well-defined borders (black arrow), perilesional hyperpigmentation (red arrow), and absent pigment network (yellow arrow)

Figure 2.

(a) Wood’s lamp evaluation of a case of unstable vitiligo with ill-defined borders. (b) Polarized dermoscopy (x10) of a case of unstable vitiligo with micro-Koebner phenomenon (yellow arrow) and ill-defined borders (red arrow)

Dermoscopic examination

Thirty-four (30.9%) study subjects had lesions with well-defined borders, and 76 (69.1%) had ill-defined borders. A reduced pigment network was seen in 24 (21.8%) lesions, and the pigment network was reversed in 35 (31.8%). Reticulate pigment network was present in 26 (23.6%), and was absent in 25 (22.7%). Thirty-six (32.7%) study participants showed perilesional hyperpigmentation. Perifollicular pigmentation was noted in 47 (42.7%). A majority (86, 78.2%) of these patients did not have satellite lesions. Micro-Koebner on dermoscopy was observed in 14 (12.7%) [Figures 1b, 2b, and 3].

Figure 3.

Polarized dermoscopy (x10) of an unstable lesion demonstrating satellite lesions (red arrow)

Based on BPLeFoSK criteria, 42 (38.2%) participants had a cutoff score of ≥1.5, and 68 (61.8%) had less than 1.5.

Correlation between VIDA score and performance of dermoscopy and Wood’s lamp evaluation

On applying the Chi-square test, a statistically significant association was obtained between the VIDA score and Wood’s lamp as well as the VIDA score and dermoscopy [Table 2].

Table 2.

Association between Vitiligo Disease Activity (VIDA) score–Wood’s lamp evaluation and VIDA score–dermoscopy

	Stable cases based on VIDA score	Unstable cases based on VIDA score	Χ2	P
Stable cases based on Wood’s lamp evaluation	18	23	13.22	0.000
Unstable cases based on Wood’s lamp evaluation	9	60
Total	27	83
Stable cases based on dermoscopy	20	22	19.53	0.000
Unstable cases based on dermoscopy	7	61
Total	27	83

Agreement between the diagnostic tests

The standard extent of agreement based on the kappa (κ) value is tabulated [Table 3]. There was a fair agreement between clinical criteria and Wood’s lamp examination (κ=0.33) (P = 0.00) as well as clinical criteria and dermoscopic criteria (κ=0.40) (P = 0.00). There was moderate agreement between Wood’s lamp and dermoscopic criteria (κ=0.55) (P value = 0.00).

Table 3.

Standard extent of kappa value based on the Landis and Koch scale

Kappa value	Landis and Koch scale
<0	Poor
0.01-0.20	Slight
0.21-0.40	Fair
0.41-0.60	Moderate
0.61-0.80	Substantial
0.81-1.00	Almost perfect

Sensitivity and specificity analysis

Wood’s lamp had a sensitivity of 72.3%, and dermoscopic evaluation using BPLeFoSK criteria with a cutoff score of 1.5 had a sensitivity of 74.1%, considering clinical criteria as the gold standard. The specificity of Wood’s lamp and dermoscopy was 66.7% and 73.5%, respectively. The ability of Wood’s lamp examination to identify clinically stable vitiligo was 87%, and to rule out the same was 43.9%. These were slightly more with dermoscopy (PPV = 89.7%, NPV = 47.6%).

ROC curve analysis (Wood’s lamp versus clinical criteria)

The area under the ROC curve plotted for Wood’s lamp examination with clinical criteria as the gold standard was 0.695.

ROC curve analysis (BPLeFoSK criteria versus clinical criteria)

The ROC curve was plotted for BPLeFoSK criteria. The area under the curve was 0.826. According to our study, to fetch a specificity of 97.6%, we need a cutoff score of 3.5 in the BPLeFoSK score.

Discussion

In our study, 27 (24.5%) had stable disease based on VIDA score. One-third of the study participants (38, 34.54%) had disease activity of <6 weeks. In the study by Nirmal et al.[14] on 131 lesions of 85 patients, 52 lesions were stable.

One-third (37.3%) of the study participants presented with well-defined borders on Wood’s lamp examination. In a study of 50 patients with vitiligo, Benzekri et al.[20] found that 29 (58%) patients had ill-defined borders, and 21 (42%) patients had well-defined borders. Nirmal and his colleagues observed that 60 of 131 lesions had a sharp border on Wood’s lamp illumination.[14] Kamath and her co-workers assessed 200 vitiligo patches in 60 patients over 6 months. They noticed that leukotrichia and satellite lesions reduced from baseline to follow-up in responsive patches, and increased in progressive patches.[15] They also noticed a statistically significant increase in the perifollicular and perilesional hyperpigmentation in responsive patches at follow-up.[15] A prospective observational study to sequentially determine the dermoscopic features of vitiligo and its association with disease activity in patients on medical treatment noted that at 8,12, and 16 weeks, satellite lesions and micro-Koebner phenomenon were significantly associated with active disease. Perifollicular pigmentation was associated with repigmenting vitiligo for 8 weeks, 12 weeks, and 16 weeks.[21]

Currently, the activity of a vitiligo lesion is assessed mainly by clinical criteria. However, we found that 12.75% of cases of vitiligo that were unstable clinically had features of stability on Wood’s lamp. Nearly one-eighth (13.65%) of cases of vitiligo that were unstable clinically had features of stability on dermoscopy. The agreement between Wood’s lamp and dermoscopic assessment was moderate. There is a paucity of studies comparing the agreement between these three diagnostic modalities.

The clinical criteria depend mainly on the history elicited from the patient. As history can be affected by recall bias, we need a tool to assess stability objectively. It is especially important as the surgical treatment can lead to Koebner phenomena and extension of disease in an unstable case. The sensitivities of Wood’s lamp (sensitivity = 72.3%) and BPLeFoSK criteria with a 1.5 cutoff score (sensitivity = 74.1%) in comparison with clinical evaluation were almost similar. However, while comparing the specificity, the BPLeFoSK score with a cutoff score of 1.5 (specificity = 73.5%) had a slightly higher specificity than Wood’s lamp (specificity = 66.7%), but this difference may not be of practical significance. As a higher specificity would ensure the prevention of Koebner after surgical procedures in vitiligo, we suggest a cutoff score of 3.5 for the BPLeFoSK criteria. This would increase the specificity to 97.6%, though with lower sensitivity – which is a more desirable scenario in this context. A higher cutoff score of 3.5 in the BPLeFoSK score is almost as good as the clinical criteria for the assessment of stability without a subjective component in it.

In our study, the area under the ROC curve plotted for Wood’s lamp versus clinical criteria was 0.695, and that for the curve plotted for dermoscopy versus clinical criteria was 0.826. The area under the ROC curve for dermoscopy versus Wood’s lamp in a previous study by Nirmal et al. was 0.95.[14] They suggested a cutoff score of 1.5 in BPLeFoSK to detect stable vitiligo with a sensitivity of 90% and a specificity of 94.4%.[14] However, this cutoff fetched only a sensitivity of 74.1% and a specificity of 73.5% in our study. There could be many reasons for this difference. Nirmal and co-workers used Wood’s lamp as the gold standard instead of the clinical criteria we used.[14] Also, they analyzed multiple vitiligo patches in the same patient. Our study had a larger sample size, too.

Limitations

Some of the limitations of this study are cross-sectional study design, examination of only one lesion in each patient, absence of blinding, lack of follow-up, absence of histopathologic examination of the lesions, lack of sequential observation by a combination of clinical, dermoscopic, or Wood’s lamp examination, and utilization of VIDA scoring system, which itself has recall bias. Using a nonvalidated scoring system is also a limitation of this study. One of the strengths of our study is that we have considered the clinical criteria as the gold standard test.

Conclusions

The important implication of our study is that if we use dermoscopy to assess stability at a BPLeFoSK cutoff score of 3.5, the selection of stable cases for surgery can be done objectively. However, to answer the question of whether we can replace clinical assessment with Wood’s lamp or dermoscopy to determine the stability of vitiligo, cohort studies comparing the outcomes of surgical procedures done in patients assessed by these three methods are necessary. Hence, we propose a cutoff score of more than or equal to 3.5 in BPLeFoSK criteria to indicate stability in vitiligo.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)

The preparation of this manuscript was carried out entirely by the author without the use of artificial intelligence technologies.

Funding Statement

Nil.