Standards of laboratory practice: evaluation of fetal lung maturity. National Academy of Clinical Biochemistry

In this standard of laboratory practice I recommend guidelines for fetal lung maturity (FLM) testing. If possible, obtain a 10-mL uncontaminated sample by amniocentesis. Keep the amniotic fluid at 4 degrees C and mix well before testing. If centrifugation is required, strictly adhere to the protocol. Most laboratories should offer a rapid test, such as fluorescence polarization, phosphatidylglycerol, or foam stability index, daily on both a routine and emergency basis. Requests for lecithin/sphingomyelin ratio may be referred to a reference laboratory. Communicate immediately the results of any FLM test to the ordering location. The report should contain the result, sample contamination, and reference information. Separate reference intervals for diabetic patients are not recommended.

Published by Clinical chemistry, 1997. The guideline itself is at the source linked here.

pubmed.ncbi.nlm.nih.gov/8990255/