Risk of human immunodeficiency virus in surgeons, anesthesiologists, and medical students

We postulated that three factors determine the occupational risk of infection from the human immunodeficiency virus (HIB) for surgeons, anesthesiologists, and medical students: first, the risk of needlestick exposure per year (range for surgeons 3.8-6.2, weighted average 4.2; range for anesthesiologists 0.86-2.5, weighted average 1.3; range for third-year medical students 0-5, best estimate 5); second, the risk of seroconversion from a needlestick exposure (0.42%-0.50%); and third, prevalence of HIV in the population served (0.32%-23.6%, depending on geographic location). Thus, the calculated range for occupational risk of HIV infection for a surgeon over a 30-yr period (assuming no change in HIV prevalence or benefit from protective measures) was 0.17%-13.9%; for an anesthesiologist, 0.05%-4.50%. The corresponding range of occupational risk for a medical student during the third year was 0.007%-0.59%. The range of risk is large because the variation in prevalence of HIV infection from one area to another is great. The authors validated the methodology first by using an equation, with estimates from the literature for factors in the equation, to calculate the risk of infection for hepatitis B and then by comparing the results with known rates of infection in the prevaccine era. Calculated occupational risk of hepatitis B infection for anesthesiologists was in the lower range of actual prevalence of infection (calculated range 2.32%-20.6%; known range 6%-26%). Calculated risk versus prevalence for surgeons was fairly close (7.31%-53.4% versus 24.4%). The prevalence of HIV infection, however, is estimated to be increasing between 4% and 8.6% annually, causing the 30-yr risk for surgeons to increase to 0.32%-0.71% in low-prevalence work sites and to 24.4%-36.4% in high-prevalence work sites. For anesthesiologists, the 30-yr risks increase to 0.10%-0.22% in low-prevalence areas and to 8.26%-13.0% in high prevalence areas; for third-year medical students, the 1-yr estimates are 0.001%-0.007% for low-risk areas and 0.12%-0.59% for high-risk areas. Double gloving reduces the risks of a needlestick exposure in surgeons by 57%-92% (average 80%). Thus, over 30 yr, the calculated occupational risks for a surgeon decrease (even assuming a 4% annual increase in prevalence of HIV infection) from 0.32% to 0.06% in low-risk areas and from 24.4% to 5.41% in high-risk areas; the risks for an anesthesiologist might similarly be postulated to decrease from 0.10% to 0.02% in low-risk areas and from 8.26% to 1.71% in high-risk areas. For a third-year medical student in a low-risk area, the decrease is from 0.0013% to 0.0003%, and for one in a high-risk area, the decrease is from 0.59% to 0.12%. Even with double gloving, these risks are substantially greater than those for other public safety officers (i.e., policemen and firemen). Geographic location, type of needlestick exposure (glancing versus puncture), and adherence to safety procedures such as double gloving may be important determinants of actual risk. Based on the published data for hepatitis B infection, the calculated risk for HIV infection may be correct for surgeons, underestimated for anesthesiologists, and still unresolved for third-year medical students. More secure estimates could be afforded if more data were available for number of needlesticks per year and for the reduction of risk by use of safety precautions. If the occupational risk of HIV infection for anesthesiologists is as great as that for surgeons, double-gloving precautions may have as great a benefit.