title: Blood test for placental site trophoblastic tumor and nontrophoblastic malignancy for evaluating patients with low positive human chorionic gonadotropin results.
abstract: OBJECTIVE
  To examine utility of measurement of proportions of free beta-subunit of human chorionic gonadotropin (hCG) in diagnosis of placental site trophoblastic tumor (PSTT) and nontrophoblastic neoplasm in patients with persistent low hCG levels and patients with history of gestational trophoblastic diseases.
  
  
  METHODS
  The USA hCG Reference Service measured proportions of free beta-subunit in 128 cases, 45 with active invasive trophoblastic disease and 83 questionable cases with persistent low hCG levels, with or without history of gestational trophoblastic disease (GTD).
  
  
  RESULTS
  High proportions of free beta-subunit (> 30% of total hCG) were identified in 18 of 128 cases, all suspected of having PSTT or nontrophoblastic neoplasm, which was reported to referring physicians. Within 2 months of testing, hysterectomy or tumor biopsy led to histologic proof of PSTT in 13 of the 18 cases and biopsy led to proof of nontrophoblastic neoplasm in 5 of the 18 cases.
  
  
  CONCLUSIONS
  We confirm use of proportion of free beta-subunit (> 30%) as a seemingly absolute test for identifying PSTT and nontrophoblastic neoplasms. It should be used to identify and diagnose these malignancies in women presenting with persistent low hCG levels outside of pregnancy and in secondary evaluation of patients with a history of GTDs.
authors: USA hCG Reference Service, Department of Obstetrics and Gynecology, University of New Mexico, Albuquerque 87131-0001, USA. larry@hcglab.com
authors: Laurence A
authors: LA
authors: Cole
authors: Sarah A
authors: SA
authors: Khanlian
authors: Carolyn Y
authors: CY
authors: Muller
mesh_terms: D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D005260:Female; D031901:Gestational Trophoblastic Disease / Q000097:blood*; D006801:Humans; D011247:Pregnancy; D018245:Trophoblastic Tumor, Placental Site / Q000097:blood*; D014594:Uterine Neoplasms / Q000097:blood*
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human