A cost-effective sample pooling strategy for line blot assay in detecting onconeural antibodies.

BACKGROUND: Onconeural antibodies are a group of autoantibodies present in patients with paraneoplastic syndromes (PNS), and are indicative for underlying malignancies. The use of indirect immunofluorescence assay (IFA) as the sole screening method for onconeural antibodies without line blot assay (LBA) could potentially miss a significant population of patients with PNS. However, testing each serum individually on LBA will pose significant economical and labour burdens to clinical laboratories. Based on the screening result from IFA, we developed a cost-effective pooling strategy for the detection of onconeural antibodies on LBA. METHODS: Results of onconeural antibodies tested by IFA and LBA from 1887 serum samples received in the Central Sydney Immunology Laboratory were retrospectively analysed. Sera were pre-screened by IFA before proceeding to LBA. Sera with positive staining on IFA were tested individually on LBA while sera with negative IFA were examined by pooling. Agreements of antibody reactivity against onconeural antigens were evaluated for sera run by pooling and by individually. The estimate of the cost saving was also conducted for the pooling strategy. RESULTS: Antibody reactivity to each specific onconeural antigen from pooling run had over 95% qualitative result agreement with sera run individually on LBA. An excellent correlation (r = 0.88) of positive reactions quantitated by band signal intensity was also observed. Using our well-established sera pooling strategy for LBA, a cost saving of 50.1% was achieved for reagent alone. CONCLUSIONS: The sera pooling strategy for LBA is a reliable and cost-effective approach for testing low prevalence diseases such as PNS.

Reproducibility of estradiol and testosterone levels in postmenopausal women over 5 years: results from the breakthrough generations study.

Prospective cohort studies examining sex hormones in relation to cancer risk have generally collected blood samples at 1 time point, with an assumption that hormone levels measured in these samples will be reliable markers of true levels at other times. In postmenopausal women, body fat is a major source of estradiol; therefore, changes in adiposity may affect the correlation of single measurements to more relevant long-term averages. To estimate the intraclass correlation coefficient (ICC) for estradiol and testosterone, we collected repeat blood samples from 119 postmenopausal women (average age = 59.4 (standard deviation, 4.7) years) from the United Kingdom during 2004-2005 and again during 2010-2011. The ICCs (adjusted for assay variation) were 0.73 (95% confidence interval: 0.63, 0.82) for total estradiol and 0.59 (95% confidence interval: 0.47, 0.72) for total testosterone. The ICCs were 3%-5% larger after adjustment for change in body mass index (weight (kg)/height (m)(2)) or leptin, which are 2 markers of change in adiposity. There was no increase in ICCs after adjustment for change in age, alcohol consumption, smoking, exercise, time between waking and blood collection, or season. The results suggest that other factors account for within-woman variation in these sex hormones.

Changes in estradiol and testosterone levels in postmenopausal women after changes in body mass index.

CONTEXT: Endogenous sex hormones are risk factors for postmenopausal breast cancer. A potential route for favorable hormonal modification is weight loss. OBJECTIVE: The objective of the study was to measure change in plasma estradiol and testosterone levels in postmenopausal women in relation to change in body mass index (BMI) and plasma leptin. SETTING: The setting was a cohort study of over 100,000 female volunteers from the general population, United Kingdom. PARTICIPANTS: The participants were a sample of 177 postmenopausal women aged over 45 years who provided blood samples during 2004-2005 and again during 2010-2011. MAIN OUTCOME MEASURE: Outcomes were percentage change in plasma estradiol and testosterone levels per 1 kg/m² change in BMI and per 1 ng/mL change in plasma leptin. RESULTS: Among women with reduction in BMI, estradiol decreased 12.7% (95% confidence interval: [6.4%, 19.5%]; P < .0001) per kg/m² and among women with increased BMI estradiol increased 6.4% [0.2%, 12.9%] (P = .042). The corresponding figures for testosterone were 10.7% [3.0%, 19.0%] (P = .006) and 1.9% [-5.4%, 9.7%] (P = .61) per kg/m². For women with decreases and increases in leptin, estradiol decreased by 3.6% [1.3%, 6.0%] (P = .003) per ng/mL and increased by 1.7% [-0.3%, 3.6%] (P = .094), respectively. The corresponding figures for testosterone were 4.8% [2.0%, 7.8%] (P = .009) and 0.3% [-2.0%, 2.6%] (P = .82) per ng/mL. CONCLUSIONS: In postmenopausal women, changes in BMI and plasma leptin occurring over several years are associated with changes in estradiol and testosterone levels. The results suggest that fat loss by an individual can result in substantial decreases in postmenopausal estradiol and testosterone levels and provides support for weight management to lessen breast cancer risk.