Reliability assessment and validation of the post-acne hyperpigmentation index (PAHPI) in a population from Sub-Saharan Africa in Senegal

BACKGROUND

A post-acne hyperpigmentation index (PAHPI) has been developed in the United States to better compare therapeutic modalities. Our aim in this study was to validate the PAHPI score in patients with skin type VI from sub-Saharan Africa.

PATIENTS AND METHODS

The study was conducted in Dakar, Senegal. Twenty-one patients with Fitzpatrick skin type VI, aged 17 to 55 years, presenting hyperpigmentation secondary to acne were included. Ongoing use of skin bleaching products or acne treatments was allowed. Four trained dermatologists rated the patients using the PAHPI. A narrow-band reflectance spectrophotometer (Mexameter MX-18, Cologne, Germany) was used to measure the degree of pigmentation of involved and adjacent skin on 6 representative facial lesions.

RESULTS

The average inter-rater reliability (weighted Kappa) showed substantial agreement for intensity (0.67), moderate agreement for number (0.53) and fair agreement for lesion size (0.28). Inter-rater reliability for the total PAHPI was excellent for both day 1 and day 2 (interclass correlation coefficient of 0.87 and 0.85, respectively; P<0.0001). Intra-rater reliability for total PAHPI ranged from 0.83 to 0.93 (P<0.0001). PAHPI scoring thus demonstrated excellent reliability both between and within raters. The association was moderate to substantial for all raters on both days (range for rho on day 1: 0.531 to 0.815; range for rho on day 2: 0.448 0.762). The correlations between the Mexameter (Courage and Khazaka) measurements and PAHPI scores showed moderate to substantial agreement.

CONCLUSION

Although tested primarily in African American women to date, PAHPI is also valid for patients from sub-Saharan Africa.

Regenerating motor neurons express Nna1, a novel ATP/GTP-binding protein related to zinc carboxypeptidases

To identify genes involved in axon regeneration, differential screening was applied to RNA isolated from spinal cord of mice subjected to sciatic nerve transection or crush injury. A 4-kb transcript, termed nna1, was identified that was rapidly induced in affected motor neurons in both paradigms. The levels of nna1 transcript levels declined in motor neurons within 1-2 weeks after nerve crush, coincident with target reinnervation. If reinnervation was blocked by nerve cut and ligation, nna1 was continuously expressed in motor neurons. In addition, in situ analysis of developing embryonic nervous tissue showed nna1 was highly expressed in differentiating neurons, but not proliferating populations. Nna1 is predicted to be a zinc carboxypeptidase that contains nuclear localization signals and an ATP/GTP binding motif. Cultured neurons transfected with green fluorescent protein (GFP)-nna1 expressed GFP-Nna1 in cytoplasmic and nuclear compartments. Thus, Nna1 may contribute to nuclear signaling events in differentiating and regenerating neurons.