Table 4. Tests with the highest rates of normal test results becoming abnormal on retesting.

Test	Normal results being repeated, n (% of normal results)	Normal repeats remaining normal, n (% of normal repeats)
Urine screening	14 (82)	4 (29)
Creatine kinase	2 (22)	1 (50)
Iron	3 (14)	2 (67)
Cholesterol	4 (6)	3 (75)
Reticulocytes	8 (29)	6 (75)
Leucocyte differential	106 (72)	82 (77)
Potassium	90 (74)	70 (78)
Glucose	73 (57)	57 (78)
Sodium	83 (75)	67 (81)
Ferritin	11 (31)	9 (82)