Skin Res Technol. 2020;26:45–49. wileyonlinelibrary.com/journal/srt © 2019 John Wiley & Sons A/S.
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45 Published by John Wiley & Sons Ltd1 | INTRODUCTION
Psoriasis is a chronic inflammatory disease affecting up to 3% of the general population. The disease is multifactorial; genetic and envi‐ ronmental factors play a role in the pathogenesis.1 Nail involvement
is observed in 10% of psoriatic patients, but the risk of occurrence of such changes during a patient's lifetime may be as high as 80%‐90%.2
Nail psoriasis has a significant negative impact on quality of life, and it may also be considered an indicator for patients at risk for future psoriatic joint damage.3,4 The severity of nail psoriasis is evaluated
using the Nail Psoriasis Severity Index (NAPSI). This index evaluates
the matrix of each nail from 0 to 4 (pitting, leuconychia, red spots in the lunula, and nail plate crumbling) and the bed of each nail from 0 to 4 (onycholysis, splinter haemorrhages, subungual hyperkeratosis and oil spot/salmon patch). Although NAPSI is an objective and re‐ producible tool for calculating the degree of nail involvement, it is time‐consuming.5
Ultrasound is a useful, non‐invasive and inexpensive imaging tool for screening superficial tissues, such as nails.6,7 Shear‐wave
elastography (SWE) is a newer, cost‐effective diagnostic ultrasound technique that assesses tissue stiffness and thickness. It has many advantages, such as real‐time B‐mode imaging, lack of operator Received: 30 April 2019
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Accepted: 27 June 2019DOI: 10.1111/srt.12762 O R I G I N A L A R T I C L E
Evaluating nail thickness and stiffness with shear‐wave
elastography in nail psoriasis: A preliminary study
Zeynep Gizem Kaya İslamoğlu
1| Emine Uysal
2| Abdullah Demirbaş
1|
Necat İslamoğlu
31Department of Dermatology, Faculty of Medicine, Selcuk University, Konya, Turkey 2Department of Radiology, Faculty of Medicine, Selcuk University, Konya, Turkey 3Department of Radiology, Van research and Education Hospital, Van, Turkey
Correspondence
Zeynep Gizem Kaya İslamoğlu, Selcuk University, Department of Dermatology Faculty of Medicine, Selçuklu, Konya 42130, Turkey.
Email: gizemislamoglu@hotmail.com
Abstract
Introduction: Psoriasis is a chronic, relapsing skin disease affecting millions of people worldwide. Nail changes have been reported to occur in up to 40% of patients with mild psoriasis and 50%‐70% with severe disease. Shear‐wave elastography (SWE) is a new non‐invasive ultrasonic technique that evaluates thickness and stiffness of tissues.
Aims: To evaluate nail plate thickness and stiffness of patients with psoriasis and de‐ termine whether there are differences among psoriatic patients with and without nail involvement, and to investigate the feasibility of using SWE in assessing this disease. Materials and Methods: Nail plate thickness and stiffness were investigated in 54 patients with psoriasis and 58 healthy controls. SWE was performed with an Aplio 500 ultrasound system.
Results: Increased nail plate thickness was observed more often in the affected nails of psoriatic patients compared to non‐affected nails of patients and controls. Stiffness was similar in both groups.
Conclusions: Our study is the first report to evaluate the SWE scores in nail psoriasis. While it may not provide reliable information for diagnosis, it can be used for fol‐ low‐up treatment.
K E Y W O R D S
dependency, and quantitative measurements.8 Elastography has
been used since the late 20th century in various diseases, such as tumours of the breast, thyroid and liver, as well as in inflammatory processes in the same organs.9 In dermatology, it has been used for
the assessment of the skin and adnexa.10
Existing studies on nail psoriasis are based on ultrasound and magnetic resonance evaluation.11‐15 To our knowledge, there is no
investigation of elastography. Therefore, the aim of this study was to evaluate the usefulness of elastography in the assessment of nail psoriasis and to indicate how it can be used in a clinical setting.
2 | MATERIALS AND METHODS
This study was approved by the Institutional Review Board (No.: 2018/241), and informed consent was obtained from all participants. A total of 54 patients diagnosed with nail psoriasis and 58 healthy controls were included in the study. Patients using a systemic or topical agent for psoriasis were excluded from the study. Healthy volunteers included subjects with no other dermatological diseases affecting the nails, no anaemia or vitamin deficiencies in their labora‐ tory tests, and no history of medication use on their nails.
All the patients were examined by a dermatologist. The macro‐ scopic changes in the nails of both hands including pitting, hyper‐ keratosis and onycholysis were identified, and the severity of nail involvement was calculated by NAPSI at baseline.5 The intensity of
psoriatic changes in the skin was assessed with the Psoriasis Area and Severity Index (PASI).16 The demographic features of all subjects
were recorded.
Measurements were taken from the most affected nail and a non‐ affected nail of each psoriatic patient. In the control group, one nail from each hand was measured. SWE was performed with an Aplio 500 ultrasound machine (Canon [formerly Toshiba] Medical Systems Corporation) using a linear array transducer (frequency 14 MHz). It provides a dynamic visual display of tissue stiffness in a variety of
clinical settings ranging from abdominal examination to visualisation of small structures. Small parts examinations. The highly accurate and reproducible tool provides fully integrated measurement and report‐ ing. The 2D‐SWE map (left side) and quality mode (right side) were examined in split‐screen mode. The quality mode, which is identified as the propagation mode (arrival time contour), is a mode in which reliable data can be obtained when the lines are parallel and smooth, and the increase in distance between the lines is parallel to the in‐ crease in elasticity. Subsequently, a 1‐mm‐diameter region of interest (ROI) was used to take measurements at three different points in the sagittal plane. The ROI was placed by the examiner exactly in the centre of the phantom target. Therefore, the depth from the phan‐ tom surface to the centre of the ROI was the same in the same mea‐ suring series. The depth of the target was known (according to the manufacturer). All measurements were recorded for stiffness using the SWV (m/s)/Young's modulus E (kPa). To reduce measurement error, every recording was repeated three times and the stiffness value was calculated by averaging the three measurements. A pad filled with an ultrasonic gel was used when the images were taken. A single radiologist conducted all evaluations. While obtaining the im‐ ages, pressure was not applied to the probe, and care was taken that the operator's hand was not moving (Figures 1, 2 and 3).
The data were analysed using SPSS (Statistical Package for the Social Sciences) version 22 for Windows. Number, percentage, mean and standard deviation were used as descriptive statistical methods for evaluating the data. The t test was used to compare the quanti‐ tative continuous data between the two independent groups. The difference between the dependent groups was analysed with the paired‐group t test. The findings were evaluated at a 95% confidence interval and at a 5% significance level.
F I G U R E 1 Screenshot of thickness (depth) measurement of a
nail per mm [Colour figure can be viewed at wileyonlinelibrary.com]
F I G U R E 2 The SWE was completed using a circular ROI. The
2D‐SWE map (left side) and quality mode (right side) are shown. The left side shows the distribution of shear‐wave velocities through the nail, red areas representing high velocities and blue/ green areas low velocities. The right side shows the modüle regularly parallel and smooth contour lines. Here, measurements are in Young's modulus E (kPa) [Colour figure can be viewed at wileyonlinelibrary.com]
3 | RESULTS
The study evaluated 108 nails of patients with psoriasis and 58 nails of controls. There was a significant relationship between gender and groups (X2 = 5.960; P = .012 < .05). Fifty‐four patients
(40 males [74.1%] and 14 females [25.9%]) with nail psoriasis and 58 healthy controls (30 males [51.7%] and 28 females [48.3%]) were included in the study. The mean age of the patient group was 48.22 ± 14.69 years, and the mean age of the healthy control group was 34.10 ± 12.32 years. Age was significantly different between the groups (t (110) = 5.523; P = .000 < .05). The mean age of the pa‐ tient group (x̄ = 48.220) was higher than the mean age of the control group (x̄ = 34.100). The disease duration of the patient group was 211.890 ± 151.411 months (min = 7; max = 600). Twenty‐six of the patients (48.1%) had a family history of psoriasis, and 28 of them (51.9%) had no family history. The demographic features of the par‐ ticipants are presented in Table 1.
In the patient group, the mean thickness of affected nails (x̄ = 1.048) was higher than the mean thickness of non‐affected nails (x̄ = 0.719; t (53) = 15.392; P = .000 < .05). However, there was no significant difference in SWE values between affected and solid non‐affected nails as according to kPa and m/s in the patient group (P > .05). The stiffness in kPa was 59.647 ± 38.813 in af‐ fected nails and 60.675 ± 39.801 in non‐affected nails. In m/s, it was 4.130 ± 1.569 in affected nails and 4.250 ± 2.078 in non‐affected nails.
The comparisons of the patient group with the healthy control group are as follows: the affected nail thickness of the patient group (x̄ = 1.048) was higher than the healthy nail thickness of the control group (x̄ = 0.703), the thickness of the non‐affected nails of the pa‐ tient group and nails of the healthy control group was similar, and there was no statistically significant difference in SWE values be‐ tween the patient group and healthy volunteers (P > .05; Table 2).
4 | DISCUSSION
To the best of our knowledge, this is the first report on the use of elastography in nail psoriasis. As a main finding, significantly higher thickness in the affected psoriatic nails compared with the non‐af‐ fected nails in patients and controls was observed. However, the stiffness of the nail plate of affected nails, non‐affected nails and nails of healthy controls was similar.
Elastography is a technique in which ultrasound is used to de‐ tect changes in the elasticity of tissues.17 When the stiffness of
tissues or organs increases, inflammatory processes have been associated with a poorer prognosis. Moreover, tissues tend to become fibrotic, or tumoural processes may occur.18 Evaluation
of elasticity of tissues could therefore enable early, non‐inva‐ sive monitoring and treatment of inflammatory and tumoural processes.10 Shear‐wave elastography is a form of elastography
which characterises shear waves. SWE detects shear‐wave dis‐ placement velocities, makes quantitative measurements and can
F I G U R E 3 Screenshot of stiffness per the SWV (m/s). Three
valid measurements were taken in all modes (m/sn or kPa) [Colour figure can be viewed at wileyonlinelibrary.com]
Patients Controls P n % n % Gender Males 40 %74.1 30 %51.7 X2 = 5.960 P = .012 Females 14 %25.9 28 %48.3
Family history of psoriasis
+ 26 %48.1 – – − 28 %51.9 – – Ort. Ss. t/P Age 48.220 14.690 34.100 12.327 5.523/.000 Disease duration (mo) 211.890 151.411 – – PASI 12.0 10.3 – – NAPSI 12.5 6.31 – –
TA B L E 1 Demographic features of the
be expressed in either kPa or m/s.19 Studies of cutaneous elastog‐
raphy consist of only small case series, and they are experimental with limited scientific validity.
Recently, several original studies have focused on importance of the elastography in dermatological diseases. Inflammation not only causes changes in the sonographic structure of the skin and adnexa in B‐mode and Doppler ultrasound, but also affects the stiffness of the structures.20 Gaspari et al showed that elastography was superior to
B‐mode ultrasound for observing stiff areas around the abscesses of patients with abscesses. Cucos et al studied 16 psoriatic plaques and measured the effects of topical corticosteroid treatment on epider‐ mal and dermal thickness and elasticity. They concluded that the sen‐ sitivity of elastography is low in evaluating the treatment response.21
In many cases with nails, ultrasound alone is sufficient without the need for further imaging assessment. However, magnetic reso‐ nance can also be used in some specific situations, especially when periungual soft tissues and bone involvement need to be further evaluated.22 In psoriasis, nail plate thickness can be useful in discrim‐
inating between patients with psoriatic nail involvement and healthy controls.14 Hypervascularity, viewed as an increase in Doppler signal,
is related to increased disease activity.12 In nail psoriasis, ultrasound
can show loss of definition of the ventral plate, thickening of the nail bed, increased blood flow on the nail bed, and loss of definition, irreg‐ ularities and undulation of both plates.12,13 Marina et al and Gisondi
et al found increased nail plate thickness in patients with psoriasis compared to healthy controls using high‐frequency sonography.12,23
Marina et al also found increased blood flow in the enlarged ves‐ sels in the nail bed, ventral nail plate deposits and irregular or totally fused nail plates in psoriatic patients compared to controls.12
The present study has some limitations. Firstly, the small sam‐ ple size of patients and controls at a single clinic does not reflect the general population. Secondly, the study mostly included cases of pitting, onycholysis and subungual hyperkeratosis, but here is a wide clinical spectrum of nail disease related to psoriasis. Thirdly, we could only use a transducer with a frequency of 14 MHz be‐ cause it was the only one available and it is used generally in many radiology clinics. Finally, this is the first study of elastography in
nail psoriasis, and for this reason, the results cannot be compared with other research.
In conclusion, this study found that patients with psoriasis have increased nail plate thickness compared to their own non‐ affected nails and controls. The stiffness of all nails according to SWE was similar. From this point of view, it can be said that the new method of SWE is inadequate to define nail diseases and may only be useful in measuring nail thickness. Perhaps by taking ad‐ vantage of this benefit, it can be used for follow‐up treatment. However, further studies using elastography in nail diseases are necessary to validate these results.
ACKNOWLEDGMENTS
None.
CONFLIC T OF INTEREST
There is no conflict of interest.
ORCID
Zeynep Gizem Kaya İslamoğlu https://orcid. org/0000‐0002‐8141‐3186
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How to cite this article: Kaya İslamoğlu ZG, Uysal E, Demirbaş
A, İslamoğlu N. Evaluating nail thickness and stiffness with shear‐wave elastography in nail psoriasis: A preliminary study. Skin Res Technol. 2020;26:45–49. https ://doi.org/10.1111/ srt.12762
