Vitamin C depletion and pressure sores EDITOR,-Helen F Goode and colleagues cite the main risk factors for pressure sores in elderly people-namely, acute illness, poor mobility, long periods on high pressure surfaces, incontinence, and confusion.' They did not control for these effects so are unwise to conclude that there is a significant association between vitamin C and the development of pressure sores in elderly subjects with femoral neck fractures, particularly since the patients were unselected. Rather than seek a "clear cut risk factor which determines why one patient should develop a sore given the same conditions as another patient," the authors could perhaps have used an instrument such as the Waterlow pressure sore assessment score.2 This instrument acknowledges that the risk of developing pressure sores is multifactorial, but its application allows an appropriate care plan to be constructed, including the allocation of equipment such as mattresses to prevent the condition arising in the first place.' Such a system is used routinely in many units caring for elderly people. MARGARET LEICESTER

I Goode HF, Burns E, Walker BE. Vitamin C depletion and pressure sores in elderly patients with femoral neck fracture. BRM 1992:305:925-7. (17 October.) 2 McLellan DL. The feasibility of indicators and targets for rehabilitation services. Clinical Rehabilitation 1992;6:55-66. 3 Ryan TJ. Diseases of the skin. In: Weatherall DJ, Ledingham JGG, Warrell DA, eds. Oxford textbook of medicine. Oxford: Oxford Medical Publications, 1987:20.98-9.

EDITOR,-Helen F Goode and colleagues' paper on the relation between vitamin C and pressure sores in elderly patients with femoral neck fracture' accords with observations published in 1969 after a controlled trial of vitamin supplementation in 80 long stay geriatric patients followed up for one year.2 Mean leucocyte ascorbic acid concentrations were 14-6 pg/108 cells in the controls and 13-6 p.g/108 cells in the treated group on entry, 27-3 and 56-5 pg/108 cells respectively at six months, and 23-6 and 57-9 Lg/108 cells respectively at 12 months. At the end of the year pressure sores were present in nine of 29 surviving controls and two of 33 survivors who had been treated (y2=6-6069, p