title: Sensitivity of over-the-counter pregnancy tests: comparison of utility and marketing messages.
abstract: OBJECTIVE
  To determine the sensitivity of seven over-the-counter pregnancy tests (OTC-PTs) using urine containing a mixture of human chorionic gonadotropin (hCG)-related molecules as found on the first day of missed menstrual period.
  
  
  METHODS
  Blinded in vitro sensitivity analysis.
  
  
  METHODS
  Medical school laboratory.
  
  
  METHODS
  None.
  
  
  METHODS
  Urine was tested with OTC-PT devices at titers of 100, 50, 25, 12.5, 6.3, and 0 mIU/mL hCG immunoreactivity, and laboratory workers rated their confidence in the test result based on whether the test result was a clear, sharp, and unquestionable band in the test window.
  
  
  METHODS
  Analytical sensitivity, defined as the urine concentration at which all OTC-PTs tested gave a positive result regardless of operator confidence score; clinical sensitivity of OTC-PTs, defined as the proportion of pregnancies likely to be detected on the first day of a missed period and calculated from the analytical sensitivity and a recently published regression curve for total urine hCG immunoreactivity in 25 urine samples from this period of gestation; percentage of tested devices showing a band in the test window at a specific hCG concentration measured devices positive; percentage faulty devices, defined as the proportion of tested devices failing to yield a band in the control window; and confidence score, determined from operator ratings for each device at each concentration of hCG.
  
  
  RESULTS
  First Response Early Result had an analytical sensitivity of 6.3 mIU/mL, which was estimated to detect greater than 95% of pregnancies on the day of missed period. The sensitivity of Clearblue Easy Earliest Results was 25 mIU/mL, which indicated detection of 80% of pregnancies. The sensitivity of the five other products was 100 mIU/mL or greater, indicating detection of 16% or less of pregnancies. Three of these last products included faulty devices.
  
  
  CONCLUSIONS
  Universal claims for OTC-PTs of more than 99% laboratory accuracy and use as early as the first day of missed period, while cleared for use by the U.S. Food and Drug Administration, are ambiguous and inappropriate for many products, according to these data. The majority of products tested were found to detect only a small percentage of pregnancies on the first day of a missed menstrual period. Until more data become available on the actual clinical sensitivity of these products, pharmacists should advise consumers to be cautious in interpreting test results.
authors.affiliation: Department of Obstetrics and Gynecology, MSC10 5580, University of New Mexico Health Sciences Center, Albuquerque 87131-0001, USA. larry@hcglab.com
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Cole
authors.forename: Jaime M
authors.initials: JM
authors.lastname: Sutton-Riley
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Khanlian
authors.forename: Marianna
authors.initials: M
authors.lastname: Borkovskaya
authors.forename: Brittany B
authors.initials: BB
authors.lastname: Rayburn
authors.forename: William F
authors.initials: WF
authors.lastname: Rayburn
mesh_terms: D000328:Adult; D006063:Chorionic Gonadotropin; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D008389:Marketing of Health Services; D011247:Pregnancy; D011258:Pregnancy Tests / Q000592:standards; D015203:Reproducibility of Results
chemical_list: D006063:Chorionic Gonadotropin