A Comparison of the Concordance of Digital Images, Live Examinations, and Skin Biopsies for the Diagnosis of Hospitalized Dermatology Consultation Patients

Noah Scheinfeld, MD, JD, Jeremy Kurz, MD, Ellen Teplitz, MD

Disclosures

Skinmed. 2003;2(1) 

In This Article

Methods

To enhance medical record keeping, we decided to image all patients referred to the dermatology consultation service from the inpatient units at the Montefiore Medical Center located in the Bronx, NY in March of 2000. Previously, for the purposes of record keeping, patients had been imaged erratically. Since imaging was part of record keeping and did not affect care it was deemed unnecessary to obtain investigational review board approval for this project. Consents for photography were obtained from all patients prior to their being imaged. A total of 58 consultations were received. Forty-eight patients consented to imaging and definitive diagnostic procedures (biopsies, potassium hydroxide preparations) were performed on 29 patients.

Patients' skin lesions were imaged with a Nikon Coolpix 950 digital camera (Nikon Corp., Tokyo, Japan) using a 3x optical Zoom-Nikkor lens equivalent to 35 mm format 38-115 mm F2.6-F4.0. The Nikon Coolpix 950 can provide images with a resolution of 1600x1200 pixels using a 2.11 million pixel charged coupled device. Images were stored in a compressed (4:1) Joint Photographic Experts Group (JPEG) format on a Compactflash media card.

In order to standardize the imaging process, specific camera settings were used. The camera automatically set shutter speed. Lens aperture was manually changed to the minimum setting (this maximized F-stop and image depth) allowed by the camera given the lighting available to maximize depth of field. The image quality was set to fine (image compression factor 1:4; approximately 1 megabyte per picture) to preserve image quality while allowing multiple pictures to be taken over the course of a day without having to download the images or change Compactflash cards. This level of image compression was preset by the camera. The camera's white balance mode was set automatically to standardize color balance. If the camera images were underexposed as determined by the student, the student attached a ring flash (Sunpak autoDX8R ring flash unit with through the lens [TTL] metering) (Tocad Co. Ltd., Japan) to the camera to increase illumination (Figure 1).

Nikon 950 Coolpix digital camera with ringflash

Images were taken in varying lighting situations because images were acquired wherever a dermatology consultation patient was located. Several photographs were taken of each patient. One photograph included the lesion (lesion location based on referring physician's description of the location and distribution of the lesion) viewed at the closest possible focal length. Larger lesions or lesions with a large distribution were imaged in two or more views. An image that encompassed the whole patient was acquired whenever possible. If the rash involved more than one area, regional images were acquired as well. Erythematous lesions were imaged, whenever possible, without and with diascopy (Figure 2).

A diascopy of a red macular rash that was diagnosed as a purpuric drug eruption by skin biopsy; live and digital diagnosis was leukocytoclastic vasculitis

The imaging, performed by a medical student who was neither a dermatologist nor a photographer, occurred on the same day as the live examination so that chronologic differences in image appearance would not account for discrepancies in diagnosis between digital and live consultation.

A standardized history was obtained from each patient, including demographic information, past medical history, medications, history of present illness, associated symptoms, and previous treatments. Also recorded were lesion location, duration, whether lesions were pruritic or painful, and whether there were other constitutional symptoms (fever, fatigue, weight loss).

Images were viewed either on the camera's 130,000 pixel LCD display and/or a PC laptop's video display with a resolution of 800 x 600 pixels. The images viewed on standard PC screens were only slightly easier to interpret when compared with images viewed on the camera's LCD screen. After viewing the images, the resident reported his differential diagnosis (up to three diagnoses) to the student who recorded them. According to the resident, screen size did not affect his ability to make a diagnosis.

For our primary outcome, we were interested in reliability or interobserver agreement. For logistical reasons, two attending dermatologists examined live patients. One examined 80% of patients and the other 20%.

Accuracy was our secondary outcome. When clinically warranted, skin punch biopsies (3-4 mm diameter) were obtained and the results were used as the standard to which the clinical dermatologic diagnoses were compared.

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