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The risk of nosocomial human immunodeficiency virus (HIV) infection among hospitalized patients comes almost exclusively from transfusion of fresh blood products. Current estimates of the risk of HIV infection from the transfusion of blood or components vary from 1/40,000 to 1/250,000 (0.0025% to 0.0004%), with the most probable likelihood estimated to be 1/153,000 (0.0007%). The major route of transmitting such HIV infection is via blood collected during the interval between infection of the donor and development of a detectable circulating antibody level to the AIDS virus (i.e., the "window period"). The current risk to hemophiliacs receiving treated coagulation factor concentrates is negligible. The risk to healthcare personnel of acquiring HIV infection from accidental puncture wounds and from handling HIV-infected blood or body fluids is 0.42% per episode. Most reported seroconversions have resulted from penetrating injuries with sharp objects contaminated with HIV-positive blood. The degree of risk to healthcare workers will vary with the community, the patient population served, and the frequency of penetrating injuries.

Antithrombin III (Human) (AT III) was administered to 18 patients with documented hereditary AT III deficiency. In eight patients with no ongoing clinical symptoms of thrombosis, the percent increase per unit AT III infused per kilogram of body weight ranged from 1.56% to 2.74%, and the half-life from 43.3 to 77.0 hours. No significant difference was noted between patients receiving and those not receiving coumarin therapy. In clinically ill patients, the in vivo recovery was significantly lower and ranged from 0.64% to 1.90% increase per unit AT III infused/kg. Efficacy of AT III was evaluated in 13 patients for the prevention or treatment of thrombosis. AT III was efficacious as assessed by the absence of thrombotic complications after surgery and/or parturition, and the nonextension and nonrecurrence of thrombosis in patients exhibiting an acute thrombotic episode. No side effects were noted. Follow-up studies indicated no hepatitis B seroconversion and no alanine aminotransferase elevations in patients who were not transfused with other blood products.

From April 22 to July 28, and from October 7 to November 3, 1985 the American Red Cross, the Council of Community Blood Centers, the American Association of Blood Banks, and the American Blood Resources Association provided the Food and Drug Administration with data at 2-week intervals on human T-lymphotropic virus type III (HTLV-III) test kit results at blood and plasma collection centers. Reports were received from over 150 blood collection centers that screened 2,502,829 units of blood for antibody to HTLV-III by enzyme-linked immunosorbent assay (ELISA) during nine 2-week surveillance intervals. Of these, 25,324 or 1.01 percent were initially reactive and 8443 or 0.34 percent were repeatedly reactive. The repeatedly reactive rate for women was 0.33 percent and for men 0.30 percent. Data for source plasma was collected at 275 locations and tested at eight central laboratories showed that for 2,603,652 units screened (which may represent multiple collections from the same donor) 3978 or 0.15 percent were repeatedly reactive. Screening results from both blood and plasma collection centers varied over time and among kits.

The risk of transmission of the human immunodeficiency virus to recipients of blood transfusions exists chiefly during the period between the time a donor is infected and the time he or she has a positive blood test for HIV antibodies. Estimating the chance that blood will be donated during this period is an effective way to define the risk of HIV infection from transfusion. Using this approach, and employing data from over 17 million American Red Cross blood donations, we estimate that during 1987 the most likely number of units of blood infected with undetected HIV that were transfused was 131 (range, 67 to 227). For a patient, the odds of contracting HIV infection were 1:153,000 per unit transfused. A patient who received the average transfusion (5.4 units) had odds of 1:28,000. The risk has been decreasing by more than 30 percent a year. We estimate that donor-recruitment practices plus careful education and screening are eliminating 49 of every 50 donors likely to be HIV-positive and that testing is 92 to 97 percent effective, for a combined effectiveness of 99.9 percent. The risk of undetected infectious units can probably be further reduced by transfusing fewer units and units from fewer donors, recruiting more women and fewer men as new donors, and encouraging more frequent donations from donors who have been tested repeatedly.