Accuracy of a home based device for giving an early estimate of pregnancy duration compared with reference methods

Capsule:
A home pregnancy test with weeks since ovulation results had 93% agreement with time since ovulation and 99% with ultrasound, which provides an estimate more accurate than last menstrual period and earlier than ultrasound.

Authors:
Sarah Johnson, Ph.D., Sonya Godbert, C.Stat., Paul Perry, Pauline Parsons, Louise Roberts, Philip Buchanan, John Larsen, M.D., Todd A. Alonzo, Ph.D., Michael Zinaman, M.D.

Volume 100, Issue 6, Pages 1635-1641.e1, December 2013

Abstract:

Objective:
To assess a home pregnancy test’s accuracy to concurrently detect pregnancy and determine pregnancy duration.

Design:
Multicenter, prospective study.

Setting:
Study sites in the United States.

Patient(s):
Women actively attempting to conceive who have menstrual bleeds (18–45 years).

Intervention(s):
Volunteers collected early morning urine samples (three or fewer menstrual cycles). Pregnant volunteers underwent ultrasound dating scans. Ovulation day (LH surge +1 day) during pregnancy-resulting cycles was determined by quantitative measurement of LH. Random urine samples were tested with the hCG-measuring pregnancy test from 4 days before the expected period until 4 weeks later.

Main Outcome Measure(s):
A home pregnancy test’s accuracy in determining pregnancy duration compared with ultrasound and ovulation day.

Result(s):
Agreement between pregnancy test results and time since ovulation was 93% (confidence interval [CI], 91.5–94.4). Agreement with ultrasound was dependent on the formula: there was 99% agreement when calculated with adjustment for Hadlock formula bias (Pexsters; CI, 98.2–99.4) or using a nonbias formula (Wu; CI, 98.6–99.6), when ultrasound error was accommodated. Agreement was lower when bias/measurement errors were not accounted for (Wu, 86%, CI, 83.9–88; Hadlock, 80.8, CI, 78.2–83.3).

Conclusion(s):
This home pregnancy test provides an accurate estimation of pregnancy duration in weeks categories, 1–2, 2–3, 3+ weeks since ovulation, thereby showing utility in dating pregnancy.

  • grassy2

    I am confused by this paper – it states that ultrasound was performed at weeks 11-13 after LMP but how can those ultrasound estimates of gestational age then be inside the windows 1-2,2-3 and 3+ weeks since ovulation (even if we add the 2 weeks follicular phase to those windows given 5 weeks or less since LMP)

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