One analytical goal that each laboratory should strive for is to make method imprecision for each analyte equal to or less than one half of the average intra-individual biological variation. Intra-individual variation is the amount that an analyte fluctuates within an individual over time. The degree of fluctuation is essentially the same irrespective of the time span of repeat measurements, instrumentation or methods used for measurement, geographic region, or patient's age. Patients with stable chronic diseases (such as renal failure, hypertension, diabetes mellitus, and liver disease) may have different set points for an analyte, but the degreee of fluctuation about the set point is the same. Because of its constancy, intra-individual biological variation data can be used by any laboratory to evaluate method performance.
Estimates of Average Intra-individual Biological Variation
Analyte |
CVi (%) |
Analyte |
CVi (%) |
ALT |
23.0 |
FSH |
2.9 m, 31 f |
Albumin |
3.0 |
GGT |
14.5 |
Aldosterone |
29.0 |
Glucose |
8 |
ALP |
8.0 |
Glucose, fasting |
4.5 |
Amylase |
10.5 |
17OHprogesteron |
10 m, 20 f |
Anion Gap |
9.5 |
IgA, G, M |
5 |
ACE |
12.5 |
Insulin |
15 |
Apolipo A1 |
6.5 |
Iron |
20 |
Apolip B |
7.5 |
LD |
13 |
AST |
8.2 |
Lipase |
14 |
Bicarbonate |
5.6 |
Magnesium |
3 |
Bilirubin, T |
18.0 |
Osmolality |
1 |
Bilirubin, D |
26 |
Phosphate |
7 |
CA-125 |
25 |
Potassium |
1.1 |
Calcium |
3.0 |
Prolactin |
7 m, 41 f |
CEA |
11.5 |
PSA |
18 |
Chloride |
1.2 |
Proteins, total |
3 |
Cholesterol, T |
6.0 |
Sodium |
0.8 |
Cholesterol, HDL |
7.0 |
Testosterone |
8 m, 8 f |
Cholinesterase, s |
5.4 |
TSH |
20 |
Cortisol |
15 |
T4, total |
7 |
CK, total |
32 |
T4, free |
6 |
Creatinine |
5 |
Transferrin |
2.3 |
DHEA-S |
1.2 m, 5.6 f |
Triglycerides |
22 |
Estradiol |
22 m, 61 f |
T3, total |
8.5 |
Ferritin |
10 |
Uric acid |
8.6 |
Fructosamine |
4.6 |
Urea |
10 |
|
