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Clinical Chemistry, Vol 16, 756-759, Copyright © 1970 by the American Association for Clinical Chemistry
1 Metabolic Laboratory and Department of Medicine
B, Hadassah University Hospital, Jerusalem, Israel.
Methemoglobin and methemalbumin markedly diminish the measurements by spectrophotometry of the change in absorbance at 450 nm (
A450)
in amniotic fluid but do not affect the chemical (diazo) determination of
bilirubin. The converse was true of hemoglobin. In 72 of 82 specimens there
was no gross contamination of amniotic fluid with these pigments and
the two types of bilirubin determination agreed well (r = 0.98, p<0.001)
when a slight modification of the Malloy-Evelyn method was used (1 volume
of amniotic fluid was diluted to 3 volumes before addition of reagents). In
the other 10 cases the presence of metheme pigments significantly decreased the
A450, but in none of the 82 specimens was there sufficient
free hemoglobin present to depress significantly the results of the chemical determination, although it can do so if enough is present.
Submitted on May 4, 1970
Accepted on May 29, 1970
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