This happens about 2-3% of the time in people with celiac disease and can lead to false-negative test results. Common tests for celiac disease include: 1  Anti-tissue transglutaminase antibody (anti-tTG), IgA: detects antibodies to tissue transglutaminase, an enzyme that causes the crosslinking of certain proteins. 2  Anti-tTG, IgA is the most sensitive and specific blood test for celiac disease.
A contour line is a line drawn on a topographic map to indicate ground elevation or depression. A contour interval is the vertical distance or difference in elevation between contour lines. Index contours are bold or thicker lines that appear at every fifth contour line.
CONTOUR INTERVAL. 1  The contour interval is the distance between each contour line. The contour interval is found along the bottom edge, center of the map. 2  When calculating the elevation of a point you should always determine the contour interval first. 3  Click here to see the contour interval of a USGS Topographic Map.