1. Apostrophes are used to show possession.
The laboratory tests were ordered by Dr. Cole’s office.
Mrs. McElroy’s condition has deteriorated significantly.
Those surgical instruments are Dr. Jones’s personal property.
Alternative: Those surgical instruments are Dr. Jones’ personal property.
2. Apostrophes are used to show singular and plural possession or ownership, notably with units of time.
She is to return to see me in one month's time.
He has had a pain in the right groin of two months’ duration.
The uterus is 16 weeks' size.
3. It’s is a contraction for it is; use of the apostrophe indicates that a letter has been omitted. Its is a possessive pronoun and does not use an apostrophe; the words it is cannot be substituted.
It’s (it is) my opinion that she has an immune disorder.
The fetus was noted to have its back to the camera on ultrasound. (Cannot substitute it is.)
4. Apostrophes are not needed when forming the plurals of abbreviations or numbers, except in abbreviations containing periods and to avoid confusion when lowercase letters or symbols are made plural.
WBCs CMTs 40s 1990s
x’s and y’s +'s M.D.’s
5. Avoid using an apostrophe and s with eponyms (something named for a person) when referring to surgical instruments and medical devices.
Fogarty catheter (not Fogarty’s catheter)
DeBakey clamp (not DeBakey’s clamp)
6. The use of the apostrophe and s with other eponyms is determined by common usage. The transcriptionist should consult a medical dictionary to determine current usage, if the dictating physician's preference is not known.
Kasai operation McBurney’s incision
Apgar score McMurray’s maneuver
Exception: Hyphenated eponyms do not use an apostrophe to show possession.
Abbe's operation Abbe-Estlander operation
Chiari's disease Budd-Chiari syndrome
7. Various medical dictionaries and style references often disagree with each other about whether a particular eponym should have an apostrophe and s to show possession; thus, in many instances there may be more than one acceptable style.
Homans sign Homans' sign
Cushing syndrome Cushing's syndrome
Babinski reflex Babinski's reflex
Graves disease Graves' disease
8. If a, an, or the precedes an eponym, it is not necessary to use the possessive apostrophe and s.
She was placed in the Trendelenburg position.
A McBurney incision was made in the right lower quadrant.
The Bassini hernia repair was accomplished without difficulty.