Centrifugal ultrafiltration method for determining the percent of free testosterone in serum

Serum free testosterone (T) % in the follicular phase of 11 normal women, 11 normal men and 30 pregnant women of 5 to 39 weeks of gestation were determined by the centrifugal ultrafiltration method (CUF), which was performed at the centrifugation of 5 minutes, 1000 g and 37 degrees C, using the Amicon MPS-3 and YMT membrane. These conditions were shown to be appropriate for measuring the free T. There was a significant correlation between the percentage of free T due to the CUF and the equilibrium dialysis method (ED) (r = 0.88, p less than 0.01). Serum free T % and free T concentrations by the CUF method were, respectively, 2.89 +/- 0.09 (SE) % and 166.3 +/- 9.8 pg/ml in normal men, 1.76 +/- 0.09% and 9.4 +/- 0.7 pg/ml in non-pregnant women and 1.14 +/- 0.03%, 22.4 +/- 1.4 pg/ml in pregnant women. Serum free T % in non-pregnant women was significantly lower than in men (p less than 0.001) and higher than in pregnant women (p less than 0.001). In the CUF method the intra-assay CV was 4.9% in women, 6.0% in men and the inter-assay CV was 5.1% in women, 6.2% in men. The CUF method was more simple, rapid and accurate on the determination of the free T in serum than the ED method.     

Empirical estimation of free testosterone from testosterone and sex hormone-binding globulin immunoassays

BACKGROUND: The growing interest in measuring blood free testosterone (FT) is constrained by the unsuitability of the laborious reference methods for wider adoption in routine diagnostic laboratories. Various alternative derived testosterone measures have been proposed to estimate FT from either additional assay steps or calculations using total testosterone (TT) and sex hormone-binding globulin (SHBG) measured in the same sample. However, none have been critically validated in large numbers of blood samples. METHODS: We analyzed a large dataset comprising over 4000 consecutive blood samples in which FT as well as TT and SHBG were measured. Dividing the dataset into samples with blood TT above and below 5 nM, using a bootstrap regression modeling approach guided by Akaike Information Criterion for model selection to balance parsimony against reduction of residual error, empirical equations were developed for FT in terms of TT and SHBG. RESULTS: Comparison between the empirical FT equations with the laboratory FT measurements as well as three widely used calculated FT methods showed the empirical FT formulae had superior fidelity with laboratory measurements while previous FT formulae overestimated and deviated systematically from the laboratory FT values. CONCLUSION: We conclude that these simple, assumption-free empirical FT equations can estimate accurately blood FT from TT and SHBG measured in the same samples with the present assay methods and have suitable properties for wider application to evaluate the clinical utility of blood FT measurements.     

诊断PADAM血清游离睾酮测定方法和界限值的研究

目的比较推算法和酶免法测定血清游离睾酮（FT）的结果,探寻FT诊断中老年男子部分性雄激素缺乏综合征（PADAM）的界限值,并评估游离睾酮指数（FTI）。方法收集129例45岁以上健康男性的血清标本,酶标免疫法测定游离睾酮（aFT）,同时测定总睾酮（T）和性激素结合球蛋白（SHBG）并代入Vermeulen公式推算游离睾酮（cFT）,对两种方法的FT值进行比较。其中60例,根据视听性刺激（AVSS）时阴茎勃起监测结果分组,计算勃起正常组cFT的参考范围。以此值为依据,对FTI进行有效性检验。结果1.cFT和FTI与年龄相关性较好,而cFT与aFT值相差有统计学意义。2.cFT：勃起正常组0.37（0.20～0.52）nmol/L,异常组0.25（0.12～0.40）nmol/L。3.FTI：cFT异常组0.15,正常组0.51。FTI敏感性97.78%,特异性58.33%。结论推算法测定血清FT较酶免法科学、准确。0.20nmol/L是cFT诊断PADAM的界限值。FTI可作为PADAM病人治疗反应的随访。     

A simple intracavitary bedside method for estimation of the P-R interval.

A simple bedside intracavitary electrocardiographic technique is described. Two electrode catheters are used: one tripolar catheter positioned across the tricuspid valve in order to record the His electrogram, and a hexapolar catheter positioned through the superior caval vein near the sinus node with the proximal electrode and 6 cm lower in the right atrium with the tip electrode. This technique allows a better analysis of intraatrial conduction, widening the interpretation of the P-A interval obtained by the His bundle electrogram.     

A simple method for the preparation of human serum albumin.

A simple method, based on ethanol fractionation, for the preparation of highly purified human serum albumin with a higher yield than that of the conventional ethanol procedures is described. It consists of two purification steps, namely, precipitation of most of the other plasma proteins from a 3-fold diluted plasma with ethanol at 42% concentration, pH 5.75 and -5 degrees C, leaving over 96% pure albumin in the supernatant, followed by isoelectric precipitation of albumin from the supernatant at pH 4.8 and -5 degrees C. The paste thus obtained was processed to the final albumin solution according to the conventional methods. The yield of the final albumin with a purity of over 99% was equivalent to 29.5 g/l of plasma representing a recovery of over 93%. The possibility of recovering other plasma proteins and the suitability for large scale preparation are also discussed.     

The assessment of bioavailable androgen levels from the serum free testosterone level

Recently, it has been concluded that measurement of the serum free testosterone level is crucial for evaluating male gonadal function. However, the extent of the decline of serum free testosterone levels with aging and the actual levels in male infertility have not yet been clearly defined. In this study, the clinical significance of serum free testosterone levels was evaluated in a total of 248 subjects, including 120 healthy adult males (54 males aged 20-39, 26 males aged 40-59 and 41 males aged more than 60), 94 infertile males, 28 male hemodialysis patients, and 6 patients with Klinefelter's syndrome. Since the serum free testosterone levels correlate significantly with serum LH and FSH levels among 120 normal adult males, it appears that free testosterone has a biological action on the organ. In the subjects aged over 60, serum free testosterone levels were significantly decreased compared with the decrease of serum total testosterone. Thus, biologically active androgen levels decreased with aging. Serum free testosterone levels tended to decrease significantly from 40 years onwards. In infertile males, serum total testosterone levels were equal to those in normal adult males, but their serum free testosterone levels were significantly lower. This decrease of serum free testosterone may be one of the causes of their hypospermatogenesis. In male hemodialysis patients, serum total and free testosterone levels were not lower than in normal adult males. It is considered that the decline of percentage of serum free testosterone levels in aged males and infertile males was caused by increased serum sex hormone binding globulin (SHBG) levels. Several workers have shown that the production of SHBG is regulated by sex steroid hormones. In this study, however, serum SHBG levels were not correlated with the E2/T ratio. We concluded that measurement of the serum free testosterone level is of value in the endocrinological evaluation of male gonadal function.     

A critical evaluation of the Mefar dosimeter.

Multicentre studies of airway responsiveness (AR) are increasingly important tools in asthma epidemiology. Because comparisons of AR are made between centres it is essential that measurement techniques are accurate and standard. This study investigated the Mefar dosimeter which is currently used in the 35 centre European Community Respiratory Health Survey (ECRHS) with the next phase currently being planned. Significant differences were found in driving pressures and aerosol outputs between the three Mefar dosimeters in the laboratory. A linear relationship was also found between driving pressure and aerosol output (R2=0.96). These differences are important as they may lead to variations between centres of < or =35% in the drug dose delivered in AR measurement, which could potentially diminish the power of individual study centres to accurately detect national differences in AR. Dosimeter driving pressure and nebulizer output should be standardized in future studies of airway responsiveness. With relatively simple quality control measures in place it is believed that the Mefar dosimeter can produce reliable between-centre longitudinal data with an increase in the accuracy of these important studies.     

Low free testosterone levels in rheumatoid arthritis.

The androgen status of 25 male patients with rheumatoid arthritis (RA) was assessed and compared with that of age matched controls with osteoarthritis (OA). Significantly reduced levels of serum free testosterone were found in the RA group. Within that group free testosterone was unrelated to all indices of disease activity measured, though it was strongly related to latex positivity. These results support the hypothesis that male sex hormones may have a protective role in RA, though prospective studies would be necessary to determine whether the relation was one of cause or effect.     

Quantitative serum free light chain assay in the diagnostic evaluation of AL amyloidosis.

We compared a new serum immunoassay for quantitation of serum free light chains (FLC) with the conventional tests for clonal immunoglobulin production: bone marrow immunohistochemistry, serum immunofixation electrophoresis, and urine immunofixation electrophoresis. Serum samples from 169 patients with AL amyloidosis and 20 controls were examined. Elevated levels of kappa-FLC and lambda-FLC were found in 94% and 93% of patients with the respective clonal disease. However, false positive elevations of kappa-FLC and lambda-FLC were found in 30% and 44% of patients with clonal disease of the other light chain subtype. We found that the FLC level was a reliable test for the diagnosis of clonal disease when the FLC kappa:lambda ratio was abnormal and was comparable to the conventional tests in patients with AL amyloidosis. After a histologic tissue diagnosis of amyloidosis, determining the type as AL amyloidosis relies on a panel of hematologic tests to determine light chain clonality and the exclusion other forms of amyloidosis.     

Free cortisol index: a rapid and simple estimation of free cortisol in human plasma.

A rapid and simple method for the estimation of free (nonprotein-bound) cortisol in human plasma is described. Total plasma cortisol (F) was determined by a competitive protein binding assay. An estimate of the saturation of Corticosteroid Binding Globulin was obtained by the use of "charcoal cortisol uptake" (CFU). "Charcoal cortisol uptake ratio" (CFUR) was defined as the ratio of the CFU of the unknown plasma to that of a reference serum pool. Free cortisol index (FFI) was calculated as (total plasma F) times (CFUR). Percent free cortisol and free cortisol concentration (FF) was determined by equilibrium dialysis at 37 C. 169 plasma samples with an F range of 0.8-61.2 mug/100 ml from 18 normal, 10 ACTH-stimulated, 17 estrogen-treated and 12 pregnant subjects were analyzed. A highly significant correlation between FFI and FF was found (r = 0.952). Inter-assay coefficients of variation were 7% for total plasma F and 3.5% for CFU. The method allows the rapid processing of large numbers of samples and can be performed on 0.2 ml of plasma.     

Determinants of serum total and free testosterone levels in women over the age of 65 years

CONTEXT: Little is known about testosterone (T) levels and their determinants in women of late postmenopausal age. OBJECTIVE: We describe levels of total and free T and selected factors that influence these levels in a random sample of older women. DESIGN: Levels of serum total T and free T by microdialysis were measured using ultrasensitive assays in 347 community-dwelling women aged 65-98 yr enrolled in the Cardiovascular Health Study. Cross-sectional analyses were performed to define factors associated with total and free T levels. RESULTS: In adjusted models: 1) total T levels declined with age until 80, whereas free T levels did not vary by age; 2) women with bilateral oophorectomy had 23% lower total T and 16% lower free T levels than those with at least one intact ovary; 3) oral estrogen users had total and free T levels that were 47% lower than never users; 4) obese women had 47% higher total T and 20% higher free T levels, and overweight women had 24% higher total T and 14% higher free T levels, than normal weight women; and 5) free T levels were 51% higher in black women. Corticosteroid users had 75% lower total T and 43% lower free T levels than nonusers. CONCLUSIONS: Bilateral oophorectomy, estrogen use, corticosteroid use, and low body mass index are independent risk factors for lower T levels in women aged 65 yr and over. Although highly prevalent in women of this age, the physiological significance of low T levels in late postmenopausal women requires further investigation.     

A simple technique for sonographic estimation of liver volume

A procedure for estimation of liver volume with the sonographic real-time technique is reported. Testing of this procedure in vitro revealed a very good linear correlation of sonographically determined liver volumes and liver volumes measured by water displacement. In an in-vivo measurement of 70 healthy subjects, a mean of 1402 ccm was determined for men and 1257 ccm for women. A statistically significant correlation was found with body weight and body surface. The method presented is simple and can be carried out in a short time during a routine examination.