Examinations and laboratory tests and studies are not in themselves abnormal, normal, negative, or positive. These adjectives apply to observations, results, or findings.  Avoid the use of "normal" and "abnormal" to describe persons' health status.

Results of cultures and tests for microorganisms and specific reactions to tests may be negative or positive. Other tests focus on a pattern of activity rather than a single feature, and hence a range of normal and abnormal results is possible. These tests include electroencephalograms and electrocardiograms, and modes of imaging such as isotopic scans, radiographic studies, and tomography.

Incorrect: The physical examination was normal.
Correct: Findings from the physical examination were normal.

Incorrect: The throat culture was negative.
Correct: The throat culture was negative for B-hemolytic streptococci.

Incorrect: The electroencephalogram was positive.
Correct: The electroencephalogram showed abnormalities in the temporal regions.

Incorrect: Serologic tests for Treponema pallidum hemagglutination, which were previously negative, are now positive.
Correct: Serologic test results for Treponema pallidum hemagglutination, which were previously negative, are now positive.
Also correct:
Serologic tests for Treponema pallidum hemagglutination, the results of which were previously negative, showed a titer of 1:80.

Exceptions:
HIV-positive men
Seronegative women
Negative node

Source: AMA Manual of style