What is the accuracy of a recently expired urine pregnancy test (UPT)?

Accuracy of Recently Expired Urine Pregnancy Tests

Do not use an expired urine pregnancy test, as the accuracy cannot be guaranteed and false-negative results may occur due to degradation of test reagents over time.

Why Expired Tests Are Unreliable

While the provided evidence does not directly address expired pregnancy tests, the fundamental principles of immunoassay testing indicate that:

• Reagent degradation occurs after expiration, which can compromise the antibodies used to detect β-hCG in urine, potentially leading to false-negative results 1
• Test sensitivity decreases with reagent deterioration, meaning an expired test may fail to detect the hyperglycosylated hCG (H-hCG) that predominates in early pregnancy (61% of total immunoreactivity in the 4th week after missed menses) 2
• Even non-expired tests have limitations, with 60% of home pregnancy tests showing poorer detection of H-hCG compared to regular hCG, and detection limits varying widely from 6.3-50 IU/L 2

Clinical Implications of Using Expired Tests

The consequences of a false-negative result from an expired test can be serious:

• Missed ectopic pregnancies pose life-threatening risks, with false-negative urine tests occurring in 1.6% of ED patients and 3.6% of those with abdominal pain or vaginal bleeding 3
• Delayed prenatal care can impact maternal and fetal outcomes 4
• Inappropriate medication exposure may occur if pregnancy is not recognized 1
• Missed gestational trophoblastic disease, which requires early diagnosis for optimal outcomes 5, 6

What To Do Instead

If only an expired test is available, follow this algorithm:

1. Obtain a fresh, non-expired urine pregnancy test as soon as possible 5
2. If clinical suspicion for pregnancy exists despite a negative expired test, obtain quantitative serum β-hCG testing, which is more reliable than urine testing 5, 7
3. Use clinical criteria to assess pregnancy probability before relying solely on any urine test result—a woman can be reasonably certain she is not pregnant if she meets specific criteria (≤7 days after normal menses, no sexual intercourse since last menses, consistent contraceptive use, ≤7 days post-abortion, or within 4 weeks postpartum) 1
4. Consider that even negative results from non-expired tests have limitations, including timing relative to last intercourse, recent delivery, or abortion 1

Critical Pitfalls to Avoid

• Never assume an expired test result is accurate, even if negative, particularly in patients with symptoms suggesting pregnancy or ectopic pregnancy 3
• Do not delay serum β-hCG testing when clinical suspicion is high, as urine tests (even non-expired) can be falsely negative in very early pregnancy or with extremely elevated β-hCG levels (as in multiple gestations or molar pregnancy) 6, 2
• Recognize that false-negatives occur even with valid tests—in one study, 171 of 10,924 patients (1.6%) with negative urine tests had pregnancy present, including 12 ectopic pregnancies 3
• Remember that most qualitative pregnancy tests require an additional 11 days past expected menses to detect 100% of pregnancies, so timing matters even with non-expired tests 5