Role of Photography in Acne Metrics*

*Adapted with permission from A. Chiang, F. Hafeez and H.I. Maibach, Skin lesion metrics: Role of photography in acne, J Dermatological Treatment, Epub ahead of print, DOI: 10.3109/09546634.2013.813010 (Jul 1, 2013)

To optimally treat acne, an accurate severity assessment is required1 and while visual assessments have relied on text descriptions, lesion counting and photographic methods, an ideal grading system would be more accurate and reproducible. Further, its ease of use, and time and monetary costs are also important. Here, the authors consider different approaches for improved acne assessments using photography.

Cook Grading

Decades ago, Cook et al.2 proposed an innovative acne grading method—the first photographic standard. Since the size and redness of lesions are not considered by enumeration, lesion counting is not as simple as it seems, and variance can be great. Therefore, to develop a precise, user-friendly and inter-grader consistent system that is capable of documentation for retrospective verification, Cook proposed an overall acne severity scale of 0–8, with reference photos and text descriptions illustrating grades 0, 2, 4, 6 and 8. Both sides of the face were simultaneously photographed by positioning the face parallel to a front-surface mirror, and a set of five reference photographs that elicited the most consistent 2–4–6 response by trained graders and panelists was selected.

This grading scheme was then used in a trial involving three treatment groups having: placebo capsules and topical placebo, oral tetracycline and topical placebo, or topical tetracycline and placebo capsules. The greatest correlation found between two judges, who assessed overall severity grades one week prior to treatment and eight weeks after treatment, were 0.785 and 0.891, respectively. Other trials confirmed that grading overall severity provided a measurement of efficacy that was more consistent between graders and more sensitive to differences between treatments than lesion counts.

However, for one study using an experimental drug, the affected lesion types required defining and counting, for comparison; for example, tetracycline was found to have greater effects on inflammatory lesions than comedonal acne. After initial efficacy trials, though, overall severity grading may be used for large-scale trials to be time-efficient. Cook therefore concluded that photographic standards were useful and reliable, aiding consistency between sessions and graders. Results showed that a 1.5-grade change constituted a clinically important difference since images are less powerful than on-site impressions—where a one-grade change indicated an important difference.

Through the years, Cook’s photographic method has been utilized and expanded. In 1985, Samuelson3 elaborated with a nine-grade scale of reference photos and text descriptions. This scale was used in a 12-week study where every two weeks, an on-site investigator evaluated patients’ conditions, as did the patients themselves, and photos of the patients were taken, which two additional reviewers retrospectively graded. At baseline, the investigator and patients assigned comparable grades but the retrospective reviewers assigned grades that were 1–2 units less severe. By week 12, all grades agreed closely but due to differences in baseline grades, the improvement was greater according to the on-site investigator and patients. Samuelson concluded that the scale is a useful tool, and that disagreement between reviewers and the investigator was due to a three-dimensional (3D) vs. flat perspective.

Leeds Technique

In 1984, Burke and Cunliffe4 presented the Leeds technique based on a clinical scale of 0–10 for overall assessment of acne severity in particular areas. Two physicians assessed patients, grading sites on their face, back and chest. Reference facial photos were provided for grades of: 0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 5.0 and 8.0. Intra-doctor grading was good, with r values for each of the doctors of: 0.92 and 0.94 on the face, 0.89 and 0.89 on the back, and 0.81 and 0.94 on the chest. Correlations between doctors were lower but still good, with r values of 0.89 for the face, 0.87 for the back, and 0.80 for the chest. In 1998, Cunliffe et al.5 revised the Leeds technique to include reference photos for each grade of: the face, from 1–12; the back, from 1–8; and the chest, from 1–8. Also, although the system does not score non-inflamed lesions, a 1–3 scale for non-inflamed acne was introduced. The authors believe the system’s attempt at quantitative assessment of acne is useful in clinics.

Modern Grading Adaptations

In 2008, Hayashi et al.6 established a photographic standard that matched lesion counts and text descriptions with the categories: mild, moderate, severe and very severe. Distribution of the counts also was analyzed, divided as: 0–5 = mild, 6–20 = moderate, 21–50 = severe, and 50+ = very severe and on half of the face. Representative photos were selected that also satisfied lesion counting-based classifications. The authors believe that standard photographs made classification more precise and adjusted for differences between estimator judgments.

The same investigators7 also evaluated the validity of these classifications by calculating the conformity of before and after grades assigned by members at dermatology meetings in Japan and Korea. Six patient photos were graded first, after which the severity classifications and standard photos were presented and the same six photos were presented in different order for grading. The conformity rate rose from 67.0% to 88.9% in Japan, and 68.0% to 79.8% in Korea. The authors concluded that the conformity of the data showed the adequacy of the grading system and believe it is a candidate for acne severity classification, at least for Asian patients.

In 2012, Tan et al.8 showed how text descriptions and photographs combined could accurately describe severity categories, which they believed would be more practical and time efficient than lesion-counting in clinical practices. The authors matched two acne scales that incorporated evaluations of the chest and back, in addition to the face, assigning images from Leeds revised5 to text description grades from category six of the Comprehensive Acne Severity Scale (CASS). Rater consensus was achieved for Leeds facial inflammatory grade 2 with CASS grade 3; inflammatory grade 4 with CASS grade 4; inflammatory grade 6 with CASS grade 4; and inflammatory grades 9–12, all with CASS grade 5. Consensus was also obtained for Leeds facial comedonal A with CASS 2; Leeds chest 7 and 8 with CASS 5; and Leeds back 7 and 8 with CASS 5. Photos in Leeds revised inadequately represented milder CASS grades 1 and 2 for facial acne, and all CASS grades of the chest and back except 5 (very severe). Thus, there is still a need for images that correspond to a categorical acne scale for the chest, back and face.

Imaging Techniques

Methods such as fluorescence, parallel- and cross-polarized photography also offer more information about conditions than clinical observation alone. Lucchina et al.9 and Pagnoni et al.10 studied fluorescence photography as a quick and simple method to demonstrate Propionibacterium acnes (P. acnes) population, as fluorescence corresponds to protoporphyrin IX production. Culture may still be necessary, where modest changes in P. acnes cannot be detected with fluorescence but fluorescence photography is a reliable, quick way to estimate suppressive effects of antibacterial agents.

Phillips et al.,11 and Rizova and Kligman1 used polarized light photography as a noninvasive and reliable method to enhance the visualization of acne and track lesion development. Parallel-polarized photography enhances surface features such as greasiness, scaling and degree of lesion elevation, while cross-polarized photography improves visibility of subsurface erythema, hyperpigmentation, small lesions and inflammation. Further, computational methods expand the use of images to track lesions, measure objective characteristics, and address inter- and intra-rater reliability issues, contributing to existing grading systems.12

In relation, in 2008, Do et al.13 studied softwarea to address position inconsistencies. By manually selecting alignment points for anatomic landmarks such as the nose tip, successive photos can be superimposed to decrease angle and framing inconsistencies. Such technologies can track the effects of acne medication on lesion lifespan and characterize the natural history of acne.

In 2012, Choi et al.14 used a 3D image analysis systemb to evaluate skin texture and acne lesions objectively, quantifying skin surface roughness and acne volumes before and after four weeks of treatment with an anti-acne cream. While acne is usually classified by diameter, for lesions with irregular shapes, volume provides more reliable criteria for classification. This image-based analysis provided opportunities to address topographical changes in skin, and should be used with additional visual assessment methods to grade severity.


Drawbacks to photography for acne-grading have been noted. For example, it does not allow for palpation to determine depth, and the minimization of small lesions, comedones and erythema. Photographs of patients with pigmented skin are also difficult to evaluate; for example, changes from healing lesions or tanning can affect grading.15 Dark skin tones also make the visualization and assessment of lesions difficult.16 Further, maintaining consistent settings such as lighting, distance to camera, framing and angles is also challenging.4 Some praise lesion counting as being more objective and accurate, despite being tedious and time-consuming.

Even so, there has been much support for a photographic standard, with tests for accuracy and clinical use. In addition, patient photos can be transferred to other physicians for a second opinion to ensure accurate diagnoses. Further, a change in counts is meaningless if the overall severity remains the same. Discrepancies between raters also increase as counts rise,17 indicating reliability issues as severity worsens, and as evaluated in a survey conducted by Tan et al.,18 severity was selected as the most important clinical feature. In clinical practice, acne severity assessment must be time-efficient and although lesion counting is important, it is largely impractical in practice. Thus, severity is often measured by qualitative methods.


Cook’s standard thus stands as a usable and objective method to assess acne severity. The reproducibility of the method also can help to decrease subject sample sizes in research. Further, it can be used to train and qualify graders. The combined experience summarized here strongly promotes the use of a photographic method, at least as an auxiliary method in phase 1 and 2 clinical trials. Lastly, the small, definitive, intra-subject documentation achieved by Cook represents major savings in resources.


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