Abstract | BACKGROUND: Falsely decreased serum alphafetoprotein (AFP) concentrations are reported in the autoDELFIA(®) hAFP immunoassay due to interference by complement. AFP is measured, using this assay, as part of second-trimester and integrated Down's syndrome screening tests. Decreased AFP concentrations increase the calculated risk of Down's syndrome; therefore falsely low AFP, due to assay interference, may artificially increase a patient's risk, and have the potential to cause false screen positive results. It was our aim to assess whether negative interference in the autoDELFIA(®) hAFP assay was a cause of very low AFP concentrations, and to examine the effect of falsely decreased concentrations on the calculated risk of Down's syndrome. METHODS: Three hundred and twenty-three sequential Down's screening serum samples with very low serum AFP concentration (<15 KU/L) using the autoDELFIA(®) hAFP immunoassay were selected and AFP re-measured using the E170 AFP immunoassay. RESULTS: Interference was detected in nine samples (from eight patients) on the basis of discordant AFP concentrations. The interference decreased following storage of samples at 4°C to deplete complement. Use of the falsely low AFP concentrations to calculate risk of Down's syndrome resulted in significantly increased calculated risk compared with complement depleted results. CONCLUSIONS: Laboratories should be aware that falsely low AFP concentrations due to complement interference may be obtained using the autoDELFIA(®) hAFP immunoassay. We have shown that falsely low AFP concentrations increase the calculated risk of Down's syndrome. This is a potential cause of false Down's syndrome screen positive results.
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Authors | Leanne Mannings, Sandy Trow, Janet Newman, Barry Nix, Carol Evans |
Journal | Annals of clinical biochemistry
(Ann Clin Biochem)
Vol. 48
Issue Pt 5
Pg. 438-40
(Sep 2011)
ISSN: 1758-1001 [Electronic] England |
PMID | 21795408
(Publication Type: Journal Article)
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Chemical References |
- alpha-Fetoproteins
- Complement System Proteins
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Topics |
- Complement System Proteins
(chemistry)
- Down Syndrome
(diagnosis)
- False Negative Reactions
- False Positive Reactions
- Female
- Humans
- Immunoassay
(methods)
- Mass Screening
(methods)
- Pregnancy
- Pregnancy Trimester, Second
- Prenatal Diagnosis
(methods)
- Risk Assessment
- alpha-Fetoproteins
(chemistry, metabolism)
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