Specimen meconium

Moore C, Jones J, Lewis D, Buchi K, Prevalence of fatty acid ethyl esters in meconium specimens. Clin Chem 2003 49 133-6. 

Note the condition of the specimen uncontaminated, bloody, meconium stained, xanthochromic, or obviously contaminated with mucus. Blood and meconium interfere with most tests. The report of the result should always list any contaminates seen. 

Several clinical outcome studies using AmnioStat have been reported. Although positive PG results are about 99% predictive of maturity, negative results are highly unpredictive (RDS develops in about 25% of cases with a negative PG, depending on the population) and are therefore not useful chnically. A positive PG result is very usefiil in low-risk pregnancies that require cesarean section. Determination of PG is also usefijl for specimens contaminated with blood or meconium. PG is not found in either blood or meconium, and therefore results are not affected by the presence of either of these contaminants. ... 

An FSI value of 0.47 or greater is interpreted as mature. In two studies, a combined total of 270 fetuses with an FSI of 0.47 or greater was reported, two of which developed RDS. In 110 fetuses with an FSI of 0.46 or less, 44 (40%) developed RDS. Thus the test appears to have more false predictions of immaturity than the L/S ratio or sur-factant/albiimin ratio. Tubes and stoppers must be clean and free of detergents to prevent false-positive readings. The final concentration of the ethanol is critical. Ethanol is hygroscopic therefore careful attention must he paid to its preparation and storage. The test should be conducted at 20 C to 25 Specimens contaminated with either blood or meconium tend to give a falsely mature result. 

Specimens containing mucus produce erratic results. More than 1% contamination with blood initially increases LBC because of the addition of platelets, but lamellar bodies are trapped m any clots that occur thus lowering the LBC by up to 20%. Moderate meconium contamination (Asgo up to 0.5) increases LBC by 5000/(iL or less. ... 

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