National Health and Nutrition Examination Survey

2011-2012 Data Documentation, Codebook, and Frequencies

Klotho - Serum (Surplus) (SSKL_G)

Data File: SSKL_G.xpt

First Published: April 2021

Last Revised: April 2022

Note: The NHANES Biospecimen Program processes were reevaluated in 2021 and 2022 to monitor quality control after a procedural error was identified. This error did not pose any risk of participant disclosure. Addressing this error resulted in the removal of some records from various stored biospecimen data files between 1999 and 2018 that did not meet program standards. After a comprehensive review of all stored specimen datasets, this data file was modified to remove records (<5% of records) that were initially included in error. No data values were altered. The sample weights and overall estimates were compared between the original and revised files. The sample weights provided with the original data release are appropriate to use with this updated data file; therefore, no new survey weights were created. The overall estimates from these files were examined and are consistent with the previous file. However, not all possible analyses were performed. For any queries related to this dataset please email the Biospecimen Program at serumplasmaurine@cdc.gov.

Component Description

Soluble alpha-Klotho is a pleiotropic protein that act as a paracrine and endocrine hormonal factor in multiple organs. Decreased alpha-Klotho levels have been associated with early aging symptoms in animal models of aging. Determination of Klotho concentrations was performed on frozen NHANES 2011-2012 samples that were received and tested during the period 2019-2020. Analyses were performed by a commercially available ELISA kit produced by IBL International, Japan.

Eligible Sample

Available pristine serum samples from 40-79 year old participants in NHANES 2011-2012 cycles, who gave consent for their samples to be used in future research, were analyzed with the IBL ELISA method.

Description of Laboratory Methodology

The Northwest Lipid Metabolism and Diabetes Research Laboratories, Division of Metabolism, Endocrinology, and Nutrition, University of Washington, performed analyses on all but four fresh-frozen (pristine) samples received from the Centers for Disease Control and Prevention.

Prior to the start of the study, an extensive validation of the IBL ELISA method for measurement of Klotho concentration in human samples was performed and the results of the Validation provided to the study investigators.

In summary, 1) the assay standard curves and the relative signals of the calibrator concentrations were consistently within the criteria specified by the manufacturer, 2) the obtained assay sensitivity was calculated to be 4.33 pg/mL while the manufacturer claimed sensitivity was 6.15 pg/mL, 3) two samples with very high and high Klotho concentrations were used at different dilution to evaluate the assay linearity. Plots of the expected vs. the obtained values, demonstrated an excellent linearity in the assay measurement range (R2 = 0.998 and 0.997, respectively), 4) the intra-assay precision obtained on two recombinant Klotho samples and two human samples exhibited a coefficient of variation of 3.2% and 3.9% for the recombinant and 2.3% and 3.3% for the human samples, 5) The same samples analyzed in duplicate over 4 different days, showed an inter-assay CV of 2.8% and 3.5% for the recombinant samples and 3.8% and 3.4% for the human samples, 5) the reference ranges were evaluated in 114 samples from apparently healthy donors and the alpha-Klotho levels ranged from 285.8 to 1638.6 pg/mL with a mean of 698.0 pg/mL.

All sample analyses were performed in duplicate according to the manufacturer’s protocol and all the results were checked to meet the laboratory’s standardized criteria for acceptability prior to being released for reporting.

Laboratory Quality Assurance and Monitoring

Samples were received on dry ice and each package was inspected by the laboratory’s receiving area personnel. Samples were scanned, data compared with those on the received electronic manifest and entered into the laboratory information system. All samples were stored at -80◦C until predefined batches of samples were daily provided to the technicians for analyses.

Samples were analyzed in duplicate and the average of the two values used to calculate the final value. Two quality control samples with low and high concentration of Klotho were also analyzed in duplicate in each ELISA plate. Results of analyses were automatically transmitted from the instrument to the laboratory Oracle Management System and results evaluated by the area supervisor. Samples with duplicate results exceeding 10% were flagged for analyses to be repeated. If the value of a quality control sample was not within the 2SD of the assigned value, the entire analytical run was rejected, and sample analyses repeated.

Analytic Notes

Demographic and Other Related Variables

The analysis of NHANES 2011-2012 laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES Demographic Files contain demographic data, health indicators, and other related information collected during household interviews as well as the sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.

Detection Limits

The assay sensitivity was 6 pg/mL. There are no Klotho specific cut-points to be used as indicators of biological age. The reference ranges evaluated in 114 samples from apparently healthy donors indicated the alpha-Klotho levels ranged from 285.8 to 1638.6 pg/mL with a mean of 698.0 pg/mL.

Exam sample weights should be used for analyses. Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.

Code or Value	Value Description	Count	Cumulative	Skip to Item
206.3 to 3456	Range of Values	2457	2457
.	Missing	2	2459

Table of Contents