The swine-flu outbreak has focused a spotlight on a shortage of technicians to run critical lab tests. Like the growing shortages of primary-care doctors and nurses, the shrinking ranks of skilled lab workers pose a potential threat to the safety and quality of health care, medical experts warn. Hospitals say it currently can take as much as a year to fill some job openings, and the American Society for Clinical Pathology says average job-vacancy rates currently top 50% in some states.