There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Detection Limits of hCG in Urine Pregnancy Tests
- The detection limits of hCG in urine pregnancy tests vary widely, ranging from 6.3 IU/L to 50 IU/L for regular hCG, as reported in a study published in 2001 1.
- The same study found that 9 out of 15 devices had poorer detection limits for hyperglycosylated hCG (H-hCG) than for regular hCG.
- Another study published in 2009 found that the average hCG level in urine at the time of detection was 6.02 IU/L, setting a sensitivity level for quantitative urine hCG tests to detect pregnancy 2.
- A study published in 2015 evaluated the analytical sensitivity of four commonly used hCG point of care devices and found that all devices were susceptible to false negative results at low concentrations of urine hCG 3.
Forms of hCG Detected in Urine
- H-hCG is the principal hCG-related molecule in pregnancy urine in the 2 weeks following the missed menses, accounting for 61% and 50% of total immunoreactivity in the 4th and 5th completed weeks of pregnancy, respectively 1.
- Regular hCG and H-hCG are both detected in urine, but the detection limits for H-hCG are often poorer than for regular hCG 1.
- The Siemens Immulite test was found to detect the degraded forms of hCG present in urine, and equally recognized urine and serum hCG 2.
Clinical Significance of hCG Detection
- hCG is nearly always detectable in serum and urine within 16 days after ovulation, making it a reliable diagnostic test for pregnancy assessment 4.
- Serial hCG testing is valuable in the evaluation of suspected ectopic pregnancy, and erroneous hCG test results can occur for several reasons 4.
- hCG is also an extremely sensitive and specific marker for trophoblastic tumors of placental and germ cell origin, and elevated serum levels of hCGbeta are strongly associated with poor prognosis in certain cancers 5.