Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
One example: Abstract: Some patients converted from ventricular fibrillation to organized rhythms by defibrillation - trained ambulance technicians(EMT - Ds) will refibrillate before hospital arrival.The authors analyzed 271 cases of ventricular fibrillation managed by EMT - Ds working without paramedic back - up.Of 111 patients initially converted to organized rhythms, 19(17 % ) refibrillated, 11(58 % ) of whom were reconverted to perfusing rhythms, including nine of 11(82 % ) who had spontaneous pulses prior to refibrillation.Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not(53 % versus 76 % , P = NS), although discharge rates were virtually identical(37 % and 35 % , respectively).Scene - to - hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome.Defibrillation - trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back - up is not available.
Solution is here: Ventricular Fibrillation
Explanation: This term is directly present in the abstract and it is one of the main topic in it. So can be chosen as the medical subject heading.

Now, solve this: Abstract: Information obtained for all persons with the acquired immunodeficiency syndrome (AIDS) reported to the Centers for Disease Control, Atlanta, includes a question about employment in a health care or clinical laboratory setting. As of May 1, 1986, a total of 922 (5.5%) of 16,748 adults with AIDS reported employment in such settings. Ninety-five percent of these health care workers belonged to recognized high-risk groups for AIDS; the proportion with "no identified risk" has not increased with time. All AIDS patients (including health care workers) who do not belong to high-risk groups are referred for further investigation. Of 88 health care workers initially reported with no identified risk, ten were from countries where heterosexual transmission is believed to play a major role; additional information was unobtainable or incomplete for 17 individuals. Of 61 persons on whom interviews or other follow-up information was obtained, 44 (73%) were reclassified. Specific occupational exposures that could be implicated as the source of human immunodeficiency virus infection were not identified for any health care workers with AIDS. A review of surveillance data supports other studies indicating that the risk of human immunodeficiency virus transmission in the occupational setting is low.
Solution:
Acquired Immunodeficiency Syndrome