Skin tone and diagnostic equity in contactless blood pressure screening: a prospective observational field evaluation of remote photoplethysmography in Nigeria.

OBJECTIVES

To evaluate diagnostic equity, feasibility and acceptability of a remote photoplethysmography-based blood pressure screening application among adults with darker skin tones in Nigeria.

DESIGN

Prospective observational multisite field evaluation.

SETTING

Three hospitals in Kebbi State, Nigeria.

PARTICIPANTS

Adults with Fitzpatrick skin types V-VI.

OUTCOME MEASURES: Feasibility, agreement, diagnostic accuracy, acceptability, and equity relevant factors including facial tribal markings and internet bandwidth, using automated cuff measurements as the reference standard and a 140 over 90 mm Hg hypertension threshold.

RESULTS

Among 306 enrolled participants, 249 (81.4%) produced usable readings. Agreement was poor (systolic mean absolute error (MAE) 15.4 mm Hg, root mean square error (RMSE) 19.9; diastolic MAE 10.9 mm Hg, RMSE 13.6). Sensitivity for threshold-based systolic and diastolic blood pressure classification was very low (systolic 0.04; diastolic 0.10), with systolic sensitivity 0.00 in Fitzpatrick type VI. Specificity was high (systolic 0.99; diastolic 0.89). Lower internet bandwidth correlated with reading failure (r = -0.69 to -0.51). While 70% of patients and over 90% of staff rated the tool favourably, technical limitations created a clear perception-performance gap. In an exploratory interaction analysis, Fitzpatrick type VI was associated with higher odds of measurement failure (OR 5.08, 95% CI 2.41 to 10.72), but there was no clear evidence that facial tribal markings modified this association (interaction OR 0.66, 95% CI 0.16 to 2.73; p=0.564).

CONCLUSIONS

Remote photoplethysmography (rPPG)-based blood pressure screening was feasible but showed inadequate performance in this darker-skinned field cohort, with critically low sensitivity. Without algorithmic recalibration for skin tone diversity and improved offline functionality, cloud-dependent rPPG systems deployed without spectrum-balanced validation may risk exacerbating diagnostic inequities in similar settings.