Which specimen type is recommended to prevent false-negative pregnancy tests?

The first morning urine specimen is the recommended type to prevent false-negative pregnancy tests due to several key factors. During the night, urine becomes more concentrated because the body is not producing urine at the same volume as during the day; therefore, early morning urine typically contains the highest levels of human chorionic gonadotropin (hCG) if a woman is pregnant.

hCG is the hormone detected by most pregnancy tests, and its levels can vary widely throughout the day. A first morning specimen can help ensure that the test is more likely to detect even low levels of hCG, which might be present shortly after conception.

Other specimen types, such as random urine, may be diluted due to higher fluid intake throughout the day and can lead to lower concentrations of hCG, increasing the chances of a false-negative result. Timed specimens may not align with the hours of peak hormone concentration, and while catheterized specimens could provide concentrated urine, their use is generally restricted to specific clinical scenarios rather than routine pregnancy testing.