Standardization of Testosterone Measurements in Humans
Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.
--
The androgen steroid hormone testosterone plays a critical role in the physiology of men and women. Testosterone can be either bound to a protein called sex hormone binding globulin (SHBG) or free, and can be detected by a blood test.
Accurate testosterone measurements are important in patient care and research. Standardization of testosterone measurements improves the reliability and accuracy of these tests.
Reference ranges
Standardization of testosterone measurements in humans is critical for patient care, translational research, and establishing clinical guidelines.
Accurate measurement of testosterone is important for the diagnosis of androgen deficiency in men, a condition that may be associated with symptoms of sexual dysfunction and muscle weakness.
It is also important for the monitoring of treatment of androgen-dependent disorders, such as polycystic ovary syndrome in women.
Standardized reference ranges are an essential part of the standardization process for a laboratory’s testing methods and enable laboratories to compare their measurements with those of other laboratories in a statistically significant manner.
The CDC testosterone standardization program develops and maintains a reference system that is used to calibrate individual assays in laboratories, and it also provides accuracy-based quality control materials for investigators and laboratories performing large epidemiological studies and clinical trials.
A standardized reference range is used to define the upper and lower limits of a laboratory’s measurement of testosterone, which helps to ensure that results are consistent among different labs. The lower limit of the standardized reference range is typically determined by an upper limit that has been established in a previous study, such as the Framingham Heart Study (FHS).
To establish harmonized testosterone reference ranges, researchers measured serum total testosterone concentrations in men from four distinct cohorts using a CDC-certified reference method. The data were then transformed using generalized additive models and Bland-Altman analyses to generate age-specific androgen-dependent reference ranges.
Interestingly, the distribution of age-adjusted testosterone concentrations across all four cohorts was highly concordant, which suggests that the reference ranges generated in each study can be applied broadly to populations. However, these age-adjusted reference ranges should be validated in longitudinal and randomized studies, where testosterone-dependent outcomes are analyzed.
In addition, a number of published studies indicate that the testosterone levels found in healthy, nonobese men may not be applicable to other populations or regions due to differences between assays, interlaboratory variability, and biological factors. This could contribute to the lack of wide-ranging testosterone reference ranges. As a result, physicians may find it difficult to diagnose hypogonadism and to monitor treatment of men with this condition.
Accuracy
Accuracy is a term used in laboratory testing to describe the degree to which repeated measurements of the same substance under similar conditions produce the same results. It is a concept that is important for many analytes, including testosterone.
Testosterone is one of the most common sex hormones measured in serum. It is used in the diagnosis of hypogonadism and androgen excess, and is also involved in fertility and sperm production. As such, the accuracy of serum testosterone measurements is an important concern for clinicians and researchers.
Over the years, multiple methods have been developed to measure serum testosterone. However, these methods have not all been uniformly standardized and may differ widely in their accuracy. This has led to uncertainty in translating testosterone measurements into clinical treatment, appropriate cutoffs for guidelines and epidemiological studies with public health impact.
To address this issue, the Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Laboratory Sciences initiated a series of activities to standardize testosterone measurements in humans using a single accuracy basis that is metrologically traceable from assay to reference material and method. The goal is to ensure that testosterone measurement results can be comparable across laboratories and at different times, as well as establishing reference ranges that translate into clinical guidelines and public health assessments.
Currently, the most commonly used methods of detecting and measuring testosterone in humans are immunoassay (IA) and mass spectrometry. These methods can be highly sensitive to differences in sample preparation and instrumentation, but their accuracy is often questionable at low concentrations. In particular, the IA method has a high level of measurement bias and low accuracy at very low testosterone concentrations.
In a study involving 149 samples of PCa patients, a significant correlation was observed between IA and MS over a broad range of concentrations, but a lower correlation was found in the hypogonadal range (11 nM). For testosterone below 0.416 nM, the IA method underestimated testosterone with a mean bias of -19.9 [95% limits of agreement: -20.7 to -60.5], while the MS method underestimated testosterone with a mean biases of -31.1% and 30.1% for testosterone 0.416 nM and E2 40.8 pmol/l, respectively.
Reliability
Reliability is the consistency or stability of a measure over time. A test's reliability is a critical component of its validity. For example, if you take the ACT test five times and get the same score every time, the test is reliable. However, if you have a thermometer that's a degree off each time you use it, the thermometer is not valid.
Reliability can be assessed by comparing a measurement to other similar measurements or to other relevant data. It can also be assessed through statistical methods. Reliability is often split into different types, such as internal and external.
A test's internal reliability can be measured by using the split-half method, which involves dividing the test in half and comparing the results. This can be done by dividing the first and second half of the test or by grouping random questions. It can also be done by comparing a single question to other questions on the test.
In order to establish the internal reliability of a test, researchers need to ensure that all parts of the test give similar results. This is usually done by administering the test to a group of people and comparing their scores.
CDC is helping immunoassay manufacturers and laboratories to calibrate their tests through the Hormone Standardization Program (HoSt) begun in 2010. HoSt provides accuracy-based quality control materials to laboratories that conduct large epidemiological studies or clinical trials, so they can monitor the accuracy of their measurements over time.
The HoSt program includes quarterly blinded challenges to assess laboratory performance and calibration stability. During these challenges, the measurement bias is compared to a desirable value of 6.4%. Those laboratories that meet this bias criterion are standardized to the CDC method.
Reliability and validity are essential to making good research and ensuring the quality of results. While reliability is the easiest to establish, validity requires more work. Reliability can be established by comparing different versions of the same measurement or by comparing the measurement to other relevant data or theory.
Interpretation
During the past decades, numerous laboratory techniques and analytical methods have been developed to measure testosterone and steroid hormones. The current gold standard in the field of hormonal chemistry is the tandem mass spectrometry (MS/MS). This technology has become the most widely used method for testosterone measurement in clinical laboratories. However, there are still a number of challenges in obtaining accurate and reliable measurements.
The Centers for Disease Control and Prevention (CDC) is leading a Hormone Standardization Program that is developing a reference system, calibrating individual assays, and verifying end-user test performance. The goal of this initiative is to improve the accuracy, reliability, and utility of clinical testosterone tests.
Testosterone is an androgen hormone that is produced mainly by the ovary. It is also metabolized by the adrenal glands. It is considered to be the main active circulating androgen hormone in humans.
This hormone is important for a number of conditions in humans, including prostate cancer. It is also a key indicator of bone health in men and women.
In addition, testosterone can be used to monitor aging males and to evaluate erectile function. It can also be measured to assess for symptoms related to the endocrine system, such as low libido or fatigue.
It can be a useful tool to identify hypogonadal men with prostate cancer before starting androgen deprivation therapy, and to select patients who will benefit from antiandrogen addition to castration or from secondary hormonal treatment, such as new drugs like abiraterone acetate (Zytiga) and MDV3100.
Unfortunately, most of the testosterone assays are not standardized, and there is a lot of variation between different laboratories. This is due to a variety of reasons, including the difficulty of obtaining sufficient amounts of testosterone in the bloodstream, the limited range of available assays, and the complexity of testing a broad spectrum of steroid hormones.
In order to overcome these limitations, a comprehensive approach is needed to improve the standardization of testosterone measurements. This involves developing a reference system, calibrating individual testosterone assays, and ensuring that they can be interpreted accurately and reliably. This effort is supported by the CDC Hormone Standardization Program, and includes input from various professional societies.
Conclusion
Testosterone is the main sex hormone in men, though women also have testosterone in smaller amounts. It plays a key role in regulating sexual function, muscle and bone strength, energy, and fertility. Its accurate measurement is essential for clinical management and research.
Despite the advances in technology that have improved steroid hormone measurement, assay variability within and across laboratories has not significantly decreased. Two factors appear to be the primary contributors: nonuniform assay calibration and lack of specificity.
The CDC Hormone Standardization Program has a goal of minimizing assay variation by providing measurement traceability to CDC reference methods and reducing the impact of factors that influence measurement accuracy, such as calibration and instrument bias. The program includes a phase one accreditation process that is designed to assure laboratory quality and provides ongoing assistance with calibration and performance evaluation.
