Measurement of Skin Induration Size Using Smartphone Images and Photogrammetric Reconstruction: Pilot Study

Digital health use in latent tuberculosis infection care: A systematic review

PURPOSE

With one-quarter of the world's population estimated to have latent tuberculosis infection (LTBI), it is important that the drop-outs from the LTBI cascade of care are minimized. Digital health technology could play an important role in case detection and treatment adherence. This study aims to evaluate the use and impact of digital health technology in LTBI care.

METHODS

A systematic literature search was conducted on six electronic databases from database inception until May 31st 2021. Studies that reported on the clinical use or economic analysis of digital health technology for LTBI care were included. Two investigators independently evaluated, extracted relevant studies, and assessed the risk of bias of using the Cochrane tools. The studies were synthesized qualitatively.

RESULTS

Fifteen articles describing 14 studies were included. Voice and/or textual reminders and synchronous video call to improve LTBI treatment adherence were the most commonly examined digital health interventions. Other interventions examined the use of mobile phones to improve the number of patients who returned for tuberculin skin test follow-up measurement (screening retention) and eLearning videos to enhance health literacy in LTBI care. The economic analysis supported the use of textual reminders in LTBI treatment as a cost-effective option for widescale implantation.

CONCLUSIONS

Despite limited evidence on the effects of digital health technologies in LTBI, available studies suggest they are at least equivalent to current practice. This means digital health can potentially supplement current practice, to constantly monitor and engage with people undergoing LTBI screening or treatment, as an initiative to ensure the provision of continuous and optimal care to all LTBI-affected individuals.

Tests for tuberculosis infection: landscape analysis

BACKGROUND

Only the tuberculin skin test (TST) and two interferon-γ release assays (IGRAs), QuantiFERON-TB Gold In-Tube and T-SPOT.TB, are currently endorsed by the World Health Organization as tests for tuberculosis (TB) infection. While IGRAs are more specific than the TST, they require sophisticated laboratory infrastructure and are costly to perform. However, both types of tests have limited performance to predict development of active TB. Tests with improved predictive performance and operational characteristics are needed.

METHODS

We reviewed the current landscape of tests for TB infection identified through a web-based survey targeting diagnostic manufacturers globally.

RESULTS

We identified 20 tests for TB infection: 15 in vitro tests and five skin tests. 13 of the in vitro tests are whole-blood IGRAs and 14 use early secreted antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10), with or without additional antigens. 10 of the tests are based on assays other than an ELISA, such as a fluorescent lateral flow assay that requires less manual operation and shorter assay time and hence is more suitable for decentralisation compared with the existing IGRAs. Four of the five skin tests use ESAT-6 and CFP-10 proteins, while the remaining test uses a new antigen that is specific to Mycobacterium tuberculosis complex.

CONCLUSIONS

New tests have the potential to improve accuracy, operational characteristics and end-user access to tests for TB infection. However, published data in various populations and settings are limited for most new tests. Evaluation of these new tests in a standardised design would facilitate their endorsement and programmatic scale-up.

A Systematic Investigation of Models for Color Image Processing in Wound Size Estimation

In recent years, research in tracking and assessing wound severity using computerized image processing has increased. With the emergence of mobile devices, powerful functionalities and processing capabilities have provided multiple non-invasive wound evaluation opportunities in both clinical and non-clinical settings. With current imaging technologies, objective and reliable techniques provide qualitative information that can be further processed to provide quantitative information on the size, structure, and color characteristics of wounds. These efficient image analysis algorithms help determine the injury features and the progress of healing in a short time. This paper presents a systematic investigation of articles that specifically address the measurement of wounds’ sizes with image processing techniques, promoting the connection between computer science and health. Of the 208 studies identified by searching electronic databases, 20 were included in the review. From the perspective of image processing color models, the most dominant model was the hue, saturation, and value (HSV) color space. We proposed that a method for measuring the wound area must implement different stages, including conversion to grayscale for further implementation of the threshold and a segmentation method to measure the wound area as the number of pixels for further conversion to metric units. Regarding devices, mobile technology is shown to have reached the level of reliable accuracy.

The mTST - An mHealth approach for training and quality assurance of tuberculin skin test administration and reading

Background

The Tuberculin Skin Test (TST) is a relatively simple test for detecting latent tuberculosis infection (LTBI) but requires regular quality assurance to ensure proper technique for administration and reading. The objective of this study was to estimate the accuracy and reproducibility of an mhealth approach (the mTST) to measure the size of swelling immediately following TST administration (TST injection bleb) and after 48–72 hours (TST induration).

Methods

Five non-clinical and one clinical reviewer measured the size of TST injection blebs, and TST indurations using smartphone acquired photos of sites of TST administration and readings in patients, or saline injections in volunteers. The reference standard was the onsite measurement (measured by an experienced TB nurse) of the actual TST injection bleb, or induration. Agreement of reviewers’ measurements with the reference standard, as well as agreement within and between reviewers, was estimated using Cohen's kappa coefficient.

Results

Using the mTST method to assess bleb size in 64 photos of different TST injections, agreement between reviewers, and the reference standard was very good to excellent (κ ranged from 0.75 to 0.87), and within-reviewer reproducibility of readings was excellent (κ ranged from 0.86 to 0.96). Using the mTST method to assess TST induration in 72 photos, reviewers were able to detect no induration (<5mm) and induration of 15mm or greater with accuracy of 95% and 92% respectively, but accuracy was only 20% and 77% for reactions of 5-9mm and 10-14mm respectively.

Conclusion

The mTST approach appears to be a reliable tool to assess TST administration. The mTST approach was accurate to read indurations of 0-4mm or 15+mm, but less accurate for reactions of 5-14mm. We believe the mTST approach could be useful for training and quality assurance in locations where on-site supervision is not possible.

Mobile phone-based evaluation of latent tuberculosis infection: Proof of concept for an integrated image capture and analysis system

BACKGROUND

The tuberculin skin test is the most widely used method for detecting latent tuberculosis infection in adults and active tuberculosis in children. We present the development of a mobile-phone based screening tool for measuring the tuberculin skin test induration.

METHOD

The tool makes use of a mobile application developed on the Android platform to capture images of an induration, and photogrammetric reconstruction using Agisoft PhotoScan to reconstruct the induration in 3D, followed by 3D measurement of the induration with the aid of functions from the Python programming language. The system enables capture of images by the person being screened for latent tuberculosis infection. Measurement precision was tested using a 3D printed induration. Real-world use of the tool was simulated by application to a set of mock skin indurations, created by a make-up artist, and the performance of the tool was evaluated. The usability of the application was assessed with the aid of a questionnaire completed by participants.

RESULTS

The tool was found to measure the 3D printed induration with greater precision than the current ruler and pen method, as indicated by the lower standard deviation produced (0.3 mm versus 1.1 mm in the literature). There was high correlation between manual and algorithm measurement of mock skin indurations. The height of the skin induration and the definition of its margins were found to influence the accuracy of 3D reconstruction and therefore the measurement error, under simulated real-world conditions. Based on assessment of the user experience in capturing images, a simplified user interface would benefit wide-spread implementation.

CONCLUSIONS

The mobile application shows good agreement with direct measurement. It provides an alternative method for measuring tuberculin skin test indurations and may remove the need for an in-person follow-up visit after test administration, thus improving latent tuberculosis infection screening throughput.