The Pennsylvania State University

Behavioral Endocrinology Laboratory Technical Notes

Salivary Estradiol Assay Performance Characteristics

Topical Outline

A.  Recovery
B.  Precision
    1.  Intra-assay Coefficients of Variation
    2.  Inter-Assay Coefficients of Variation
C.  Linearity of Dilution
D.  Sensitivity

A.  Recovery:

A saliva sample was spiked with 2 different levels of Estradiol and assayed.

Sample Endogenous (pg/mL) Added (pg/mL) Expected (pg/mL) Observed (pg/mL) Recovery (%)
           
I .247 .825 1.072 .989 92.3%
           
II .247 2.475 2.722 2.969 109.0%

B.  Precision:

1.  The intra-assay precision was determined from the mean of 14 replicates each.

Sample N Mean (pg/mL) Standard Deviation (pg/mL) Coefficient of Variation (%)
         
High 10 4.91 .139 2.83%
Mid 10 .671 .040 5.91%
Low 10 .216 .023 10.61%

2.  The inter-assay was determined from the mean average of duplicates for 5 separate runs.

Sample N Mean (pg/mL) Standard Deviation (pg/mL) Coefficient of Variation (pg/mL)
         
Low 5 .503 .074 13.62
High 5 5.06 .082 4.39

C.  Linearity of Dilution

Four samples were diluted with PBS and assayed.

Sample Dilution Factor Expected (pg/mL) Observed (pg/mL) Recovery (%)
I        
      6.123  
  1:2 3.028 2.777 91.7%
  1:4 1.514 1.364 90.1%
         
II        
      3.285  
  1:2 1.640 1.602 97.7%
         
III        
      1.784  
  1:2 .892 .837 93.8%
         
IV        
      1.807  
    .904 .749 82.8%

D.  Sensitivity

The lower limit of sensitivity was determined by interpolating the mean minus 20 SD for 10 sets of duplicates at the 0 pg/mL standard.  The minimal concentration of Estradiol that can be distinguished from 0 is .25 pg/mL.

The Pennsylvania State University Behavioral Endocrinology Laboratory