Webster's New World Medical Dictionary

fire supplies kit
See 
disaster supplies.
first do no harm
A classic slogan that is used in
medicine, often in the Latin wording 
primum non
nocere 
that is attributed to Hippocrates.
first stage of labor
The part of labor when the
cervix dilates fully, to approximately 10 centimeters
in diameter. Also known as the stage of dilatation.
FISH
Fluorescence in situ hybridization, a molec-
ular cytogenetic technique that tags genetic material
fifth disease
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with fluorescent molecules. FISH is useful for iden-
tifying chromosomes and parts of chromosomes,
deciphering chromosome rearrangements, detect-
ing chromosome abnormalities, and detecting and
mapping genes. For example, a FISH probe to chro-
mosome 21 allows the detection of cells with tri-
somy 21 (an extra chromosome 21, which is the
cause of Down syndrome).
fishbowl granuloma
See 
granuloma, fishbowl.
Fisher’s exact test
A statistical test used to deter-
mine whether there is a nonrandom association
between two variables that is much used in medical
research. It tests the independence of rows and
columns in a 2 
×
2 contingency table (a table with
two horizontal rows crossing two vertical columns,
creating four places for data) based on the exact
sampling distribution of the observed frequencies.
Hence it is an “exact” test.
fish-odor syndrome
An inborn error of metab-
olism that is associated with an offensive body odor
whose scent is similar to the smell of rotting fish.
Fish-odor syndrome is due to the excessive excre-
tion of trimethylamine (TMA) in urine, sweat, and
breath. This syndrome is caused by a mutation in
the gene for the enzyme flavin-containing monooxy-
genase-3 (FMO3). Dietary modifications to reduce
the consumption of triethylamine precursors may
provide some relief of symptoms. Also known as
trimethylaminuria.
fistula
An abnormal passageway between organs,
vessels, or other structures that are not normally
connected. For example, an anal fistula is an open-
ing in the skin near the anus: This opening may lead
to a tunnel into the rectal canal or to a passage that
ends in a blind pouch.