A 25-year-old man was found dead at home by the partment manager, who had been called by the decedent’s employer because of failure to report to work for the past 3 days. An external examination by the medical examiner showed splinter hemorrhages under the fingernails and no signs of trauma. The gross appearance of the heart at autop- sy is shown in the figure. Which of the following laboratory findings is most likely to provide evidence for the cause of his disease?