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.
To make topographic maps easier to read, every fifth contour line is an index contour. Because it's impractical to mark the elevation of every contour line on the map, the index contour lines are the only ones labeled.The index contours are a darker or wider brown line in comparison to the regular contour lines.o make topographic maps easier to read, every fifth contour line is an index contour. Because it's impractical to mark the elevation of every contour line on the map, the index contour lines are the only ones labeled.