50 Shades of Bald and Grey- How to Reliably Measure Scalp Hair Density and Greying

Abstract

Aims: To assess the reliability, usability, convenience, and accuracy of tools for the measurement or classification of hair density and hair greying.

Methods: Literature was extracted from five databases. The PRISMA reporting guidelines were employed. From each eligible article, the scale name, accuracy, & usability was extracted as was the inter-observer reliability and/or intra-observer repeatability which were categorised as ‘Poor’, ‘Moderate & Acceptable’, or ‘Good & Excellent’. The scale was ‘convenient’ if it required minimal equipment, and the time required was not excessive.

Results: For hair density, 11 eligible articles assessed the reliability of 13 hair density assessment tools. The tools were divided into three groups: 1Categorical (pictorial) scales: Both the Hamilton-Norwood Scale and Basic and Specific classification had ‘Poor’ inter-observer reliability, intra-observer repeatability, and usability. The Sinclair scale had a ‘Moderate & Acceptable’ intra-observer repeatability; there was no data for inter-observer reliability. All three scales were convenient, and accuracy was not reported. 2Semi-quantitative scales: There was ‘Good & Excellent’ inter-observer reliability and intra-observer repeatability for both the ‘Scalp Coverage Score’ (SCS) and ‘Dermoscopy-derived semi-quantitative hair density scales’. The latter was convenient but accuracy wasn't reported. Usability wasn't reported for either scale. The SCS was accurate but inconvenient. 3Quantitative scales: Both manual (phototrichogram assisted) and automated hair counts (TrichoScan®) had ‘Good & Excellent’ inter-observer reliability and intra-observer repeatability. Both were inconvenient however usability wasn't reported. The TrichoScan® was inaccurate. The ‘Graying Severity Score’ was the only eligible hair greying assessment tool. It had a ‘Good & Excellent’ inter-observer reliability, however, was inconvenient. Accuracy and usability were not assessed.

Conclusions: For assessing hair density clinically, the SCS and the Dermoscopy-derived semiquantitative scales are reliable tools, with the latter being more convenient although accuracy wasn't reported. The only hair greying tool, the ‘Graying Severity Score’, was reliable but clinically impractical.