Pan-Thames survey of occupational exposure to HIV and the use of post-exposure prophylaxis in 71 NHS trusts.

OBJECTIVES: To review the management of occupational exposure to definite or suspected HIV-infected blood, following the introduction of the 1997 UK Department of Health guidelines on the use of post-exposure prophylaxis. METHODS: Cross-sectional telephone survey of protocols in 71 NHS Trusts in the Pan-Thames region. Retrospective postal survey of the management of each definite or suspected HIV blood exposure between 1 July 1997 and 30 June 1999. RESULTS: Sixty-two (93%) Trusts had a written protocol, with many specialties involved in exposure management. Twenty-four Trusts reported 171 occupational exposures to definite or suspected HIV-infected blood. Of 97 definite HIV exposures, eight (8%) were discovered on post-incident HIV testing of the source patient; to which most source patients agreed when approached. Seventy-two (74%) exposed health care workers started prophylaxis and 49 (68%) completed the recommended 4-week course. Only half of those whose exposures occurred more than 6 months ago were known to have had a follow-up HIV test. CONCLUSIONS: Although most Trusts have implemented the Department of Health's guidance, collecting data on individual exposures proved difficult. We suggest that a designated department in each Trust co-ordinates and records HIV exposure management. Routine HIV testing is acceptable to most source patients and is appropriate in areas with a high prevalence of HIV seropositivity.

A survey of the use of post-exposure prophylaxis for occupational exposure to human immunodeficiency virus.

The objective of this study was to review the appropriateness of the use of post-HIV exposure prophylaxis for incidents involving occupational exposure to body fluids. The design was a retrospective analysis of the 32 incidents for which at least one dose of post-exposure prophylaxis was given, reported to the occupational health department of a London teaching hospital between 20 August 1997 and 20 January 1999. The main outcome measures were the proportion of prescriptions for exposure to a known HIV positive source, and criteria for prescribing when the source patient's HIV status was unknown. Only 31% of prescriptions were for exposure to a known HIV positive source. The reasons for prescribing post-exposure prophylaxis in the other 69% of cases were unclear. Safety data for short courses of anti-retroviral drugs in this setting could help to assess the appropriateness of their use to allay anxiety in healthcare workers, pending clarification of the source patient's HIV status. Closer collaboration between departments and more detailed guidance would improve consistency of practice, and may save some unnecessary prescriptions for expensive and toxic drugs.

Diffusion kinetics and optical waveguiding properties of outdiffused layers in lithium niobate and lithium tantalate.

Increases in the extraordinary refractive index sufficient to produce single and multimode optical waveguides have been produced by the outdiffusion of lithium oxide from the surfaces of lithium niobate and lithium tantalate crystals. The outdiffusion kinetics have been studied in detail by optical interferometry. The data fit a diffusion model for which the vaporizing surface flux is constant with time. For lithium niobate, the activation energy for diffusion is 68 +/- 1.2 kcal/mol and does not vary with orientation. However the gradient of refractive index change at the surface is larger for diffusion normal to the c-axis than parallel to the c-axis. Activation energies for vaporization of 71 kcal/mol and 59 kcal/mol were calculated from the model for diffusion perpendicular and parallel to the c-axis, respectively. The evaporation coefficient, alpha, was estimated to be less than 10(-4) with alpha perpendicular/alpha || approximately 3 so vaporization is surface reaction limited. For lithium tantalate, the activation energy for diffusion is 51 +/- 6 kcal/mol and also does not vary with orientation. The activation energy for vaporization, Q(upsilon), is approximately 63 kcal/mol and, within experimental error, is quite similar to that for lithium niobate. These values of Q(upsilon) indicate that the major vaporization species are probably lithium ions and oxygen ions. The characteristics of graded index waveguides are discussed and compared with those of slab guides. It is shown that in many respects the behavior of the two types is equivalent. We have produced a single-mode guide in lithium niobate with an effective thickness of 12 microm. Effective thicknesses as small as 6 microm are possible in lithium tantalate.