Stop chasing the whitening endpoint in pigmented skin

Design

prospective randomised, evaluator-blinded, split-face trial, three sessions at six-month intervals

Population

30 Asian patients with Fitzpatrick skin types III to V and acquired bilateral naevus of Ota-like macules

Primary outcome

clearance on the Global Aesthetic Improvement Scale, with post-inflammatory hyperpigmentation and scabbing

Effect

clearance comparable (both above 3.85/4); post-inflammatory hyperpigmentation 4.8% versus 22.6% and scabbing 9.5% versus 61.9% (both P<0.05)

Thirty Asian patients with Fitzpatrick skin types III to V and acquired bilateral naevus of Ota-like macules had three sessions of 755-nm picosecond alexandrite laser at six-month intervals, in a randomised, evaluator-blinded, split-face design. One side was treated to the conventional endpoint of immediate whitening, using a smaller spot and higher fluence. The other used a larger spot and lower fluence chosen by a melanosome-disruption threshold model, deliberately stopping short of whitening.

Clearance was equivalent — both sides scored above 3.85 out of 4 on the Global Aesthetic Improvement Scale after three sessions. The difference was entirely in harm. Post-inflammatory hyperpigmentation occurred in 22.6% of whitening-endpoint sides against 4.8% of non-whitening sides (P<0.05), and scabbing in 61.9% against 9.5% (P<0.05). Sixty-eight per cent of patients preferred the non-whitening side.

The immediate whitening endpoint is taught, expected and easy to see, which is why it persists. This trial says that in pigmented skin it is a marker of excess energy rather than of adequate treatment — the melanosomes are already being disrupted at a fluence that does not produce it. Every patient acted as their own control, on the same face, in the same session, which is about as clean a comparison as laser work allows.

This matters more in India than almost anywhere. Most of the dermal melanocytosis treated here is in Fitzpatrick IV and V skin, post-inflammatory hyperpigmentation is the complication patients most fear and most often abandon treatment over, and a 22.6% rate is the difference between a course completed and a course dropped.

• Drop immediate whitening as your endpoint for dermal melanocytosis in Fitzpatrick III to V skin
• Use a larger spot size at lower fluence rather than a small spot at high fluence
• Tell patients before the first session that no whitening does not mean nothing happened — expectation is the main barrier
• Track scabbing as a quality signal; 61.9% versus 9.5% is visible in your own follow-up clinic
• Keep the six-month interval; the equivalence shown here was across three sessions, not a faster course

The statistics, in plain English

The split-face design is what gives this its weight: each patient's two sides share skin type, sun exposure, aftercare and adherence, so the comparison is free of the confounding that sinks most laser studies. Thirty patients is small for detecting a small difference, but the differences here are large — 22.6% against 4.8%, and 61.9% against 9.5% — which is why they reach significance at this size. Equivalence of clearance is the weaker claim: a trial of 30 could miss a modest efficacy gap, and both scores sitting above 3.85 out of 4 leaves little room on the scale to detect one.

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