Factors influencing the number needed to excise: excision rates of pigmented lesions by general practitioners

To identify doctor and patient characteristics associated with excision of benign versus malignant pigmented skin lesions.

Retrospective audit of data on 4741 pigmented skin lesions excised from November 1998 to February 2000 by 468 general practitioners (39% response rate) from 223 practices in Perth, WA. (The data used were from the baseline period of a randomised controlled trial of a diagnostic aid for pigmented skin lesions.)

The number needed to treat (NNT), defined as the number of pigmented lesions needed to be excised to identify one melanoma, in relation to demographic characteristics of GPs and patients.

Relatively more benign lesions were excised per melanoma (NNT = 83) in the youngest patients (aged 10-19 years) compared with the oldest (aged > or = 70) (NNT = 11) (P [trend] < 0.001), in females (NNT = 37) compared with males (NNT = 23) (P = 0.02), and in the most socioeconomically disadvantaged (NNT = 60) compared with the least disadvantaged group (NNT = 20) (P [trend] < 0.001). The most recently graduated GPs excised more benign lesions for each melanoma (NNT = 59) than the least recently graduated (NNT = 22) (P [trend] = 0.01).

GPs could raise their threshold for excising pigmented lesions in patients who are young, female, or from areas of low socioeconomic status, or if the GPs themselves are recent graduates.