A 22-year-old woman experiences a sudden onset of severe lower abdominal pain. Physical examination shows no masses, but there is severe tenderness in the right lower quadrant. A pelvic examination shows no lesions of the cervix or vagina. Bowel sounds are detected. An abdominal ultrasound scan shows a 4-cm focal enlargement of the proximal right fallopian tube. A dilation and curettage procedure shows the only decidua from the endometrial cavity. Which of the following laboratory findings is most likely to be reported for this patient?

Conditions predisposing to ectopic pregnancy include chronic salpingitis (which may be caused by gonorrhea, but a culture would be positive only with acute infection), intrauterine tumors, and endometriosis. In about half of the cases, there is no identifiable cause. Gestational trophoblastic disease associated with a triploid karyotype with partial mole developing outside the uterus is rare. Candida produces cervicitis and vaginitis and is rarely invasive or extensive in immunocompetent patients. Syphilis is not likely to produce a tubal mass with acute symptoms (a gumma is a rare finding).