Clinical Briefs

By Louis Kuritzky, MD, Clinical Assistant Professor, University of Florida, Gainesville. Dr. Kuritzky is a consultant for GlaxoSmithKline and is on the speaker's bureau of GlaxoSmithKline, 3M, Wyeth-Ayerst, Pfizer, Novartis, Bristol-Myers Squibb, AstraZeneca, Jones Pharma, and Boehringer Ingelheim.

Does Aspirin Work Differently in Women than Men?

Although aspirin (ASA), particularly low-dose ASA 81 mg/d (LD-ASA), is well established as an appropriate agent for secondary prevention of cardiovascular disease, recent results from the Women's Health Study (WHS) about the impact of ASA in primary prevention came as a surprise: LD-ASA provided a 24% reduction in stroke, but no reduction in MI. Theorists suggested that perhaps, since MI impact has been demonstrated to be much more favorable in men than in women, there is a difference in responsiveness of platelet reactivity to LD-ASA between the sexes. To investigate this hypothesis, the platelet reactivity of at-risk men and women (n = 1,282) was measured 14 days after daily LD-ASA treatment. The at-risk group was selected from a pool of healthy individuals who had siblings with documented early CHD endpoints, but had no manifest coronary artery disease themselves. Presumably, this is a higher risk group, in whom it would be wise to be able to better define the benefits of primary prevention.

After 14 days, platelet aggregation in response to arachidonic acid stimulation (the blockade of which is the proposed mechanism by which LD-ASA prevents CVD) was equally affected in men and women. The reason(s) for the apparent differential effects of LD-ASA on CVD in men versus women remain uncertain: it is apparently not due to a diminished responsiveness of women's platelets to the antiaggregation effects of LD-ASA.

Becker DM, et al. JAMA. 2006;295:1420-1427.

Is There Something About Air Travel Besides Immobilization that Increases Risk of DVT?

That deep venous thrombosis (DVT) can occur after air flight is not a new observation, having been first reported in the 1950s. Recent data have singled out very long flights (8 hours or greater) as being remarkably more important for DVT risk than shorter flights. Generally, risk for DVT with air flight has been simply attributed to only one of the 3 characteristics of Virchow's Triad: stasis (due to immobility). Schreijer et al studied the impact of clotting factor activation associated with air flight.

To differentiate simple immobilization 'on the ground,' from immobilization with air flight, study subjects were divided into 3 groups: a real 8-hour plane flight, an 8-hour period of immobilization while watching successive movies, or the control of 8 hours of normal daily activities. The 71 men and women participated in 2 cross-over periods, so that all subjects experienced all 3 group activities.

Several coagulation factors were monitored. After flight, thrombin-antithrombin complex was elevated (indicating increased thrombotic activation), but not after 8 hours of movie immobilization or daily activities. Coagulation activation was most marked in women on oral contraceptives who had known factor V Leiden at baseline. The authors postulate that the hypobaric hypoxia encountered in flight explains the coagulation activation. Advice to avoid protracted immobility on long flights can be helpful, but may not be fully protective, since other mechanisms in addition to immobility appear to be etiologic.

Schreijer AJ, et al. Lancet. 2006;367:832-838.

The Dermatologic Nikolskiy Sign: How Good is it?

Pv Nikolskiy was a Russian dermatologist who published information about pemphigus foliaceus in 1896. He was the first to describe an altered structural integrity of the epidermis in pemphigus. The Nikolskiy Sign (also commonly spelled 'Nikolsky') is performed by placing pressure upon skin adjacent to tissue involved with bullae. In pemphigus, because the attachments of the intraepidermal intercellular bridges are damaged, skin pressure will allow the bulla to dissect further within the epidermis, as the layers separate due to IgG-mediated attachment defects. Although at one time considered specific to pemphigus, Nikolsky Sign has been sometimes reported in association with other skin disorders, such as toxic epidermal necrolysis, mycosis fungoides, and epidermolysis bullosa.

To study the sensitivity and specificity of the Nikolsky Sign, patients (n = 127) with a variety of bullous lesions were tested. The sensitivity for diagnosis of pemphigus by Nikolsky sign was only 38%. Disorders other than pemphigus also manifest Nikolsky sign. A positive Nikolsky sign is useful to support the diagnosis of pemphigus, but is also seen in other disorders.

Uzun S, Durdu M. J Am Acad Dermatol. 2006;54:411-415.