Zwangerschapstesten

In this article, we discuss possible explanations for the discrepancy in results between urine and blood pregnancy tests. The first patient, a 26-year-old woman, had breast tenderness, was tired and suffered from abdominal pain. A urine pregnancy test was negative, but blood human chorion gonadotropin (hCG) concentration was 455 U/l (reference value < 6 U/l). It was concluded that the patient was pregnant and she was followed in the outpatient clinic. Three days later she suffered blood loss and her hCG levels returned to normal. The diagnosis was a spontaneous abortion. The second patient, a 45-year-old woman, complained of abdominal pain, nausea and more blood loss than with a normal period. The urine pregnancy test was negative, but the hCG level in her blood was 470.000 U/l. Echography showed a thickened, irregular endometrium. A molar pregnancy was suspected and curettage was performed. The hCG level dropped initially but had increased at follow-up. Persistent trophoblastic disease was suspected and the patient underwent additional treatment.

Conflict of interest: none declared. Financial support: none declared.

Casus 1

Patiënt A, een 26-jarige vrouw, komt bij de huisarts omdat ze denkt dat ze zwanger is en buikpijn heeft. De uitslag van de zwangerschapstest in urine, uitgevoerd door de huisarts, is negatief. De hCG-concentratie in bloed, dezelfde middag gemeten, is 455 U/l (referentiewaarde voor vrouwen: < 6 U/l). De huisarts concludeert dat deze patiënte zwanger is.

Bent u het eens met de conclusie van de huisarts?

1a Nee, er is sprake van een laboratoriumfout bij de hCG-meting in bloed.
1b Ja, de uitslag van de urinetest is fout-negatief door interferentie of door verdunde urine.
1c Ja, de…