Fetal lung maturity assessment by a modified A650 determination.
This paper presents an evaluation of a modified absorbance method for estimating fetal lung maturity. Absorbance at 650 nm in combination with a two-step centrifugation procedure was used in an attempt to focus more directly on lamellar bodies and evaluate the contribution of residual absorbance due to non-lamellar body materials. Absorbance values after centrifugation at 250 X g for 5 minutes (A250) and 10,000 X g for 20 minutes (A10,000) were taken as estimates of total absorbance due to lamellar bodies plus non-lamellar body material and that due to non-sedimentable, non-lamellar body material respectively. These values were used to generate two new parameters: delta A (A250-A10,000), to better estimate absorbance due to lamellar bodies, and %A (delta A/A250 X 100), to express lamellar body absorbance in terms of total observable absorbance and thereby minimize effects of dilution. The three parameters (A250, delta A, %A) were used in combination to create a battery (ABatt) of absorbance values for each fluid sample. Absorbance after centrifugation at 2,000 X g for 10 minutes (A2,000), a widely used standard method, was also evaluated for purposes of comparison. A250 was designated as mature if greater than or equal to 0.350, delta A was called mature if greater than or equal to 0.250, and %A was considered mature if greater than or equal to 75%. If any of the parameters was immature, ABatt was called immature. The range of values for A250, A2,000, and A10,000, increased with gestational age in the total population as well as the corrected population (excluding amniotic fluid contaminants, and pregnancies with isoimmunization or diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)
M F
MF
Koszalka
C H
CH
Blomquist
D J
DJ
Lakatua
D000653:Amniotic Fluid / Q000032:analysis; D002498:Centrifugation; D005260:Female; D005325:Fetal Organ Maturity; D005865:Gestational Age; D006801:Humans; D008168:Lung / Q000196:embryology*; D010713:Phosphatidylcholines / Q000032:analysis; D011247:Pregnancy; D013109:Sphingomyelins / Q000032:analysis
D010713:Phosphatidylcholines; D013109:Sphingomyelins