Value of Procalcitonin Measurement for Early Evidence of Severe Bacterial Infections in the Pediatric Intensive Care Unit.

OBJECTIVES: To determine whether peak blood procalcitonin (PCT) measured within 48 hours of pediatric intensive care unit (PICU) admission can differentiate severe bacterial infections from sterile inflammation and viral infection and identify potential subgroups of PICU patients for whom PCT may not have clinical utility. STUDY DESIGN: This was a retrospective, observational study of 646 critically ill children who had PCT measured within 48 hours of admission to an urban, academic PICU. Patients were stratified into 6 categories by infection status. We compared test characteristics for peak PCT, C-reactive protein (CRP), white blood cell count (WBC), absolute neutrophil count (ANC), and % immature neutrophils. The area under the receiver operating characteristic curve was determined for each biomarker to discriminate bacterial infection. RESULTS: The area under the receiver operating characteristic curve was similar for PCT (0.73, 95% CI 0.69, 0.77) and CRP (0.75, 95% CI 0.71, 0.79; P = .36), but both outperformed WBC, ANC, and % immature neutrophils (P < .01 for all pairwise comparisons). The combination of PCT and CRP was no better than either PCT or CRP alone. Diagnostic patterns prone to false-positive and false-negative PCT values were identified. CONCLUSIONS: Peak blood PCT measured close to PICU admission was not superior to CRP in differentiating severe bacterial infection from viral illness and sterile inflammation; both PCT and CRP outperformed WBC, ANC, and % immature neutrophils. PCT appeared especially prone to inaccuracies in detecting localized bacterial central nervous system infections or bacterial coinfection in acute viral illness causing respiratory failure.

Salivary but not blood cortisol excretion is associated with metabolic biomarkers in healthy young women.

OBJECTIVES: Elevated and suppressed concentrations of cortisol have been linked with less favorable metabolic biomarkers, such as elevated lipids and glycosylated hemoglobin (HbA1c). Based on recent work reporting that some individuals secrete more cortisol into saliva (high saliva-to-blood cortisol ratio; high secretors) than others after correcting for blood cortisol concentrations, our objectives were to examine (1) whether lipids and glycosylated hemoglobin varied across cortisol and salivary secretor status; and (2) if blood and saliva provide the same results with respect to metabolic markers. METHODS: Matched saliva and dried blood spot (DBS) specimens collected once a week for four weeks (N = 48 healthy women, 192 specimens) were assayed for cortisol. Fasting blood specimens collected once from each woman were quantified for cholesterol (total, HDL, LDL), triglycerides and HbA1c. RESULTS: Low salivary cortisol secretors showed significantly higher triglyceride and HbA1c compared to high-secretors (P<0.05; t-test). The only significant correlation with mean blood or salivary cortisol concentration was a negative correlation between salivary cortisol and HbA1c (P = 0.021, r = -0.333). CONCLUSIONS: Triglycerides, HDL, and especially HbA1c were associated with salivary cortisol secretor status but not with DBS cortisol concentrations. These results suggest that blood and saliva cortisol measures might provide different health outcome information, and that salivary cortisol secretor status may provide additional information on health status. Am. J. Hum. Biol. 28:539-544, 2016. © 2016 Wiley Periodicals, Inc.

Successful hunting increases testosterone and cortisol in a subsistence population.

Controversy over the adaptive significance of male hunting in subsistence societies hinges on the relative importance of familial provisioning and mate-quality signalling. This paper examines the proximate and ultimate motivations of hunting behaviour from a neuroendocrine perspective, using salivary testosterone and cortisol data collected before, during and after hunting focal follows from 31 Tsimane hunters aged 18-82 years. Despite circadian declines in hormone levels, testosterone and cortisol of Tsimane hunters increased at the time of a kill, and remained high as successful hunters returned home. Previous studies of hormonal changes during competitions find that high-stakes and success in the presence of relevant audiences result in increased neuroendocrine arousal. If men hunt primarily to provision their families, then an additional audience would not be expected to impact testosterone or cortisol, nor would the size of the animal killed. However, if signalling male quality by 'showing off' was a larger relative driver of men's hunting behaviour, one would expect greater hormonal response in cases where men returned with large sharable kills, especially in the presence of community members. Consistent with provisioning models of male hunting motivation, neither kill size nor encountering an audience of villagers while returning from hunting was associated with hormonal changes for successful hunters.

Age-independent increases in male salivary testosterone during horticultural activity among Tsimane forager-farmers.

Testosterone plays an important role in mediating male reproductive trade-offs in many vertebrate species, augmenting muscle and influencing behavior necessary for male-male competition and mating-effort. Among humans, testosterone may also play a key role in facilitating male provisioning of offspring as muscular and neuromuscular performance are deeply influenced by acute changes in testosterone. This study examines acute changes in salivary testosterone among 63 Tsimane men ranging in age from 16-80 (mean 38.2) years during one-hour bouts of tree-chopping while clearing horticultural plots. The Tsimane forager-horticulturalists living in the Bolivian Amazon experience high energy expenditure associated with food production, have high levels of parasites and pathogens, and display significantly lower baseline salivary testosterone than age-matched US males. Mixed-effects models controlling for BMI and time of specimen collection reveal increased salivary testosterone (p<0.001) equivalent to a 48.6% rise, after one hour of tree chopping. Age had no effect on baseline (p=0.656) or change in testosterone (p=0.530); self-reported illness did not modify testosterone change (p=0.488). A comparison of these results to the relative change in testosterone during a competitive soccer tournament in the same population reveals larger relative changes in testosterone following resource production (tree chopping), compared to competition (soccer). These findings highlight the importance of moving beyond a unidimensional focus on changes in testosterone and male-male aggression to investigate the importance of testosterone-behavior interactions across additional male fitness-related activities. Acutely increased testosterone during muscularly intensive horticultural food production may facilitate male productivity and provisioning.

Physical competition increases testosterone among Amazonian forager-horticulturalists: a test of the 'challenge hypothesis'.

The challenge hypothesis posits that acute increases in testosterone (T) during male-male competition enhance performance and survivability while limiting the physiological costs of consistently high T. Human challenge hypothesis research focuses on young men in industrial populations, who have higher baseline T levels than men in subsistence populations. We tested whether the Tsimane, pathogenically stressed forager-horticulturalists of the Bolivian Amazon, would express acute T increases in response to physical competition. Saliva was collected from 88 Tsimane men (aged 16-59 years) before and after a competitive soccer match. Tsimane men had significantly lower baseline levels of T (ß = -0.41, p < 0.001) when compared with age-matched United States (US) males. Linear mixed-effects models were used to establish that T increased significantly immediately following competition (ß = 0.23, p < 0.001), remaining high 1 h later (ß = 0.09, p = 0.007); equivalent to 30.1 and 15.5 per cent increases in T, respectively. We did not find larger increases in T among winners (p = 0.412), although T increases were positively associated with self-rated performance (ß = 9.07, p = 0.004). These results suggest that despite lower levels of T than US males, Tsimane males exhibit acute increases in T at the same relative magnitude reported by studies in industrialized settings, with larger increases in T for those who report better individual performance.

Salivary concentration of progesterone and cortisol significantly differs across individuals after correcting for blood hormone values.

Between-individual variation of salivary progesterone (P4) and cortisol levels does not always closely reflect blood hormone concentrations. This may be partly a function of individual differences in salivary hormone excretion. We tested whether time of day at sampling and ethnicity contributed to individual variation in salivary hormones after adjusting for blood hormone levels. Forty-three Caucasian and 15 Japanese women (18-34 years) collected four sets of matched dried blood spot (DBS) and saliva specimens across a menstrual cycle (N = 232 specimen sets). Linear fixed-effects (LFE) models were used to estimate the effects of diurnal variation and ethnicity on salivary P4 and cortisol while adjusting for DBS levels. For each hormone, women with exclusively positive or negative residuals (unexplained variance) from the LFE models were categorized as high- or low-saliva-to-DBS hormone ratio (SDR; high or low salivary secretors), respectively. We found that salivary P4 (P < 0.05) was significantly higher in early morning compared to the afternoon, after controlling for DBS levels, ethnicity, and BMI. After further adjusting for this diurnal effect, significant individual variation in salivary P4 and cortisol remained: sixteen and nine women, respectively were categorized as low or high salivary secretors for both hormones (P < 0.001), suggesting systematic individual-specific variation of salivary hormonal concentration. We conclude that when saliva is used to quantify P4 or cortisol levels, time of day at sampling should be controlled. Even with this adjustment, salivary P4 and cortisol do not closely mirror between- individual variation of serum P4 and cortisol in a substantial proportion of individuals.

Sensitivity and specificity of C-reactive protein and α(1) -acid glycoprotein for episodes of acute infection among children in Kilimanjaro, Tanzania.

OBJECTIVES: Biomarkers of inflammation, including C-reactive protein (CRP) and α(1) -acid glycoprotein (AGP), have tremendous potential in anthropological, public health, and nutrition research as objective indicators of acute infection; however, their usage is limited by the lack of widely agreed upon, reliable cutpoints to define infection. We assessed the sensitivity and specificity of CRP and AGP for identifying acute infectious disease (ID) episodes among children in the Kilimanjaro region of Tanzania. METHODS: Data were available from 43 3- to 5-year-old children. CRP and AGP were measured in capillary whole dried blood spots (DBS). Two-week morbidity history interviews with children's primary caregivers were used to detect recent episodes of acute ID. Specimens and morbidity history interviews were collected from each child on one (n = 13) or two (n = 30) occasions for 73 paired interviews and specimens. RESULTS: We evaluated CRP and AGP for identifying acute infection (report of fever, diarrhea, or vomiting in the last week): CRP ≥ 1.1 mg/l had sensitivity of 57.14% and specificity of 86.44%; AGP ≥ 0.76 g/l had sensitivity of 57.14% and specificity of 72.41%. The combined definition (AGP ≥ 0.76 g/l or CRP ≥ 1.1 mg/l) had sensitivity of 71.43% and specificity of 70.69%. CONCLUSIONS: Among children in Kilimanjaro, Tanzania, assessed in whole blood stored as DBS, AGP ≥ 0.76 g/l or CRP ≥ 1.1 mg/l provided the best definition of acute infection. Whether this definition is appropriate for use in other populations remains to be determined.

A randomized controlled trial evaluating the effect of an internet-based cognitive-behavioral program on anxiety symptoms in a community-based sample of adolescents.

Adolescents' use of online resources to self-manage anxiety is growing. The objective of the current trial was to assess the effectiveness of an online, primarily self-led cognitive behavioral therapy (CBT) program in reducing anxiety symptoms compared to an active comparator, access to anxiety resources on a static website. A total of 563 adolescents (13-19 years) with self-identified anxiety concerns were enrolled. Self-reported anxiety symptoms were assessed pre- and post-intervention (6 weeks). Adolescents were further assessed 3 months post-intervention. Other outcomes assessed at the three time-points were quality of life (QOL) and healthcare utilization. Both interventions reduced anxiety symptoms after use. Group differences in symptom change were not significant post-intervention (p = 0.16), but were at 3 months (favouring online CBT; p = 0.04) with male participants reporting more symptom change (p = 0.03). Across time-points, as anxiety symptoms decreased, QOL increased (p < 0.001). Among participants that provided healthcare utilization before and after intervention use, the greatest changes in use were among online CBT users particularly for mental health provider visits (psychiatrist, -41.0 % vs. +18.5 %; social worker, -42.5 % vs. -22.1 %), hospital-based care (emergency department visits, -80.0 % vs. +79.4 %; hospital admissions, -76.1 % vs. +42.9 %), and use of self-help or alternative treatments (-60.0 % vs. +6.6 %). Results suggest that, over time, use of online CBT by adolescents can result in improved anxiety symptoms and fewer use of other healthcare resources compared to traditional online information seeking.

The effects of a long-term psychosocial stress on reproductive indicators in the baboon.

Psychosocial stress is thought to negatively impact fecundity, but human studies are confounded by variation in nutrition and lifestyle. Baboons offer a useful model to test the effect of prolonged mild stress on reproductive indicators in a controlled setting. Following relocation from social groups to solitary housing, a previously documented stressful event for nonhuman primates, daily urine samples, tumescence, and menstrual bleeding were monitored in twenty baboons (Papio sp.) for 120-150 days. Specimens were assayed for estrone conjugates (E1C), pregnanediol-3-glucuronide (PDG), follicle-stimulating hormone (FSH), and cortisol. Linear mixed effects models examined (1) the effects of stress on frequency of anovulation, hormone levels, tumescence and cycle length, and (2) the relationship of cortisol with reproductive indicators. Despite cortisol levels indicative of stress, anovulation was negligible (1% in 102 cycles). PDG, FSH, cycle length, and tumescence declined during the first four cycles, but began recovery by the fifth. Cortisol was negatively associated with FSH but not associated with PDG, E1C or tumescence. Ovulation, E1C, and luteal phase length were not affected. Tumescence tracked changes in FSH and PDG, and thus may be a useful indicator of stress on the reproductive axis. Elevated cortisol was associated with reduced FSH, supporting a model of cortisol action at the hypothalamus rather than the gonad. After four to five menstrual cycles the reproductive indicators began recovery, suggesting adjustment to new housing conditions. In conclusion, individual housing is stressful for captive baboons, as reflected by cortisol and reproductive indicators, although ovulation, a relatively direct proxy for fecundity, is unaffected.

Responsiveness of the reproductive axis to a single missed evening meal in young adult males.

OBJECTIVES: The male reproductive axis is responsive to energetic deficits, including multiday fasts, but little is known about brief periods of fasting (<24 hours). Reduced testosterone in low-energy balance situations is hypothesized to reflect redirection of resources from reproduction to survival. This study tests the hypothesis that testosterone levels decrease during a minor caloric deficiency by assessing the effects of a single missed (evening) meal on morning testosterone in 23 healthy male participants, age 19-36. METHODS: Participants provided daily saliva and urine samples for two baseline days and the morning following an evening fast (water only after 4 PM). Testosterone, cortisol, and luteinizing hormone were measured with enzyme immunoassays. RESULTS: Fasting specimens had significantly lower overnight urinary luteinizing hormone (P = 0.045) and morning salivary testosterone than baseline (P = 0.037). In contrast to morning salivary testosterone, there was a significant increase in overnight urinary testosterone (P = 0.000) following the evening fast, suggesting an increase in urinary clearance rates. There was a marginal increase in overnight urinary cortisol (P = 0.100), but not morning salivary cortisol (P = 0.589). CONCLUSION: These results suggest the male reproductive axis may react more quickly to energetic imbalances than has been previously appreciated.

Coital Frequency and the Probability of Pregnancy in Couples Trying to Conceive Their First Child: A Prospective Cohort Study in Japan.

Background: Low fertility persists but remains unexplained in Japan. We examined whether the probability of pregnancy was influenced by coital frequency, age, reproductive age (assessed by antimüllerian hormone, AMH), and BMI. Methods: We established a two-year prospective study with a sample of hormonally monitored Japanese women aged 23-34 years wanting to conceive their first child. For a maximum of 24 weeks participants recorded menstrual bleeding, sexual intercourse, ovulation, and pregnancy. Additional information on pregnancy and infertility treatment was collected one and two years after intake. Results: The natural conception rate and coital frequency were both low in this sample. Among 80 participants, 44% (35) naturally conceived in 24 weeks. After two years, 74% (59) of women had delivered or were currently pregnant, 50% (40) due to natural and 24% (19) due to assisted conception, and 5% (4) were lost to follow-up. By two years, 56% (45) of women had sought fertility treatment. In 18% (58/319) of the observed ovarian cycles across 24 weeks there was no intercourse in a fertile period. Higher coital frequency at intake was associated with increased probability of conception by 24 weeks of follow-up (OR 1.23, 95%CI 1.02, 1.47). Chronological age, reproductive age, and BMI were not associated with the probability of pregnancy at 24 weeks. Conclusions: Our results suggest that first, natural conception rates could potentially increase with more frequent and well timed intercourse, and second that further work is needed to understand why even in a motivated sample of women monitoring their fertile periods, both the conception and coitus rates were low.

Total and unopposed estrogen exposure across stages of the transition to menopause.

Detailed characterization of estrogen dynamics during the transition to menopause is an important step toward understanding its potential implications for reproductive cancers developing in the transition years. We conducted a 5-year prospective study of endogenous levels of total and unopposed estrogen. Participants (n=108; ages 25-58 years) collected daily urine specimens for 6 months in each of 5 consecutive years. Specimens were assayed for estrone-3-glucuronide (E1G) and pregnanediol-3-glucuronide. Linear mixed-effects models were used to estimate exposure to total and unopposed estrogen by age and reproductive stage. Reproductive stage was estimated using menstrual cycle length variance. E1G mean area under the curve and mean E1G 5th and 95th percentiles represented total estrogen exposure. An algorithm identifying days of above-baseline E1G that coincided with the days of baseline pregnanediol-3-glucuronide was used to identify days of unopposed estrogen. Mean E1G area under the curve increased with age in the pretransition and early transition and decreased in the late transition. Ninety-fifth percentile E1G levels did not decline until after menopause, whereas 5th percentile levels declined from the early transition to the postmenopause. The number of days of unopposed estrogen was significantly higher during the transition compared with the pretransition. Given the length of time women spend in the transition, they are exposed to more total and unopposed estrogen than has been previously appreciated. Coupled with epidemiologic evidence on lifetime exposure to estrogen, these results suggest that variation in the amount of time spent in the transition may be an important risk factor for reproductive cancers.

C-reactive protein across the menstrual cycle.

C-reactive protein (CRP) is a widely used, sensitive biomarker of inflammation. Studies conducted among users of exogenous hormones suggest that estrogen increases CRP, whereas progesterone decreases CRP. Examinations of CRP in normally cycling women suggest the opposite: CRP is negatively associated with endogenous estrogen and positively associated with endogenous progesterone. This work evaluates the association between menstrual cycle-related hormone changes and events (menstruation and ovulation) and CRP. Eight female subjects gave urine and blood samples from twelve days across the menstrual cycle, for a total of eleven cycles. Blood samples were assayed for CRP; urine samples for beta-follicle stimulating hormone (betaFSH), pregnanediol 3-glucuronide (PDG), and estrone glucuronide (E1G). Ovulation day was estimated using hormone levels. Presence or absence of menses was reported by subjects. Analyses were conducted with random-effects linear regression. All cycles were ovulatory; day of ovulation was identified for nine cycles. A ten-fold increase in progesterone was associated with a 23% increase in CRP (P = 0.01), a ten-fold increase in estrogen was associated with a 29% decrease in CRP (P = 0.05), and menses was associated with a 17% increase in CRP (P = 0.18); no association between ovulation or FSH and CRP was found. Hormone changes across the menstrual cycle should be controlled for in future studies of inflammation in reproductive-age women.

Effect of the Procalcitonin Assay on Antibiotic Use in Critically Ill Children.

We retrospectively studied the effect of introducing procalcitonin into clinical practice on antibiotic use within a large academic pediatric intensive care unit. In the absence of a standardized algorithm, availability of the procalcitonin assay did not reduce the frequency of antibiotic initiations or the continuation of antibiotics for greater than 72 hours.

Monitoring reproductive aging in a 5-year prospective study: aggregate and individual changes in luteinizing hormone and follicle-stimulating hormone with age.

OBJECTIVE: This study describes age-related changes in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in a 5-year prospective study of reproductive aging. DESIGN: Participants (n = 156 college-educated, white, US women; 25 to 58 y) were recruited from the TREMIN Research Program on Women's Health. They collected daily urine specimens for 6 months in each of 5 consecutive years. Specimens were assayed for LH and FSH. Aggregate changes were calculated in LH and FSH with age, and multilevel models were used to estimate individual hormone trajectories and within-woman and between-woman variances by age. RESULTS: Aggregate LH levels increased beginning after age 45; FSH increased at all ages, accelerating after age 45. Individual-level patterns with age included the following: reproductive-age LH and FSH levels, with increasing FSH and increasing or decreasing LH (ages 20 to 49); rapidly increasing LH and FSH (ages 40 to 59); and increasing or steady postmenopausal LH and FSH (ages 46 to 62). FSH levels were consistently high in the latter category, but LH levels overlapped with levels found in younger women (<45 y). Individual LH patterns showed more variability (5% to 35% of total variance) than FSH (3% to 22% of total variance). Both hormones had relatively low variation within individuals compared with between-woman differences (65% to 97% of total variance). CONCLUSIONS: Aggregate-level data do not reflect differences across women and oversimplify the age-related increases and variability in LH and FSH. Individual FSH levels are not distinguishable from reproductive-age levels until after rapid perimenopausal increases in FSH occur; individuals vary in whether their postmenopausal LH levels are distinguishable from reproductive-age levels.

Urinary beta-luteinizing hormone and beta-follicle stimulating hormone immunoenzymometric assays for population research.

OBJECTIVE: We developed assays for measurement of urinary betaLH and betaFSH under collection and storage conditions typical of non-clinical research settings. DESIGN AND METHODS: IEMAs for free betaLH and total betaFSH were validated by standard methods. Stability of urinary betaLH and betaFSH was tested across freeze-thaws and stored long term at 4 degrees C or -20 degrees C, or short term at room temperature, and with heating to dissociate the subunits. RESULTS: The IEMAs exhibited acceptable parallelism, specificity, recovery (averaging 100% for betaLH, 97% for betaFSH), imprecision (maximum within-run and between run CVs, respectively, 4.8% and 25.7% for betaLH, 5.6% and 17.0% for betaFSH), and minimum detectable dose (2.5 pmol/L for betaLH, 6.8 pmol/L for betaFSH). Urine and serum measures were highly correlated (r=0.95 for LH, 0.86 for FSH). There was no consistent decline with any storage type. Dissociation of subunits by heating was needed for betaLH, but not betaFSH. CONCLUSION: These IEMAs measure free betaLH and total betaFSH, overcoming inter-individual variability in, and collection and storage effects on, subunit dissociation, without the need for urine preservatives.

Monitoring reproductive aging in a 5-year prospective study: aggregate and individual changes in steroid hormones and menstrual cycle lengths with age.

OBJECTIVE: We describe a 5-year prospective study of reproductive aging, and present analyses of steroid hormone and menstrual cycle changes with age. DESIGN: Participants were college-educated white women, primarily of northern European ancestry, recruited from the Tremin Research Program on Women's Health (n = 156, 25-58 years). In each of 5 consecutive years, they collected daily urine specimens for 6 months and recorded menstrual bleeds for all months. Urine specimens were assayed for estrone-3-glucuronide (E1G) and pregnanediol-3-glucuronide (PDG), urinary metabolites of estradiol and progesterone. Using multilevel models, we estimated hormone and cycle-length trajectories for individual women and within- and between-woman variance by age. RESULTS: At the aggregate level, PDG declined beginning in the 30s, E1G increased into the 40s before declining, and cycle length became more variable with age. Individual-level models revealed substantial hormonal variation across women, in both absolute levels and rates of change. Most women showed declining E1G by the late 40s, declining PDG in the 30s, and increasing mean cycle length in the 40s. Hormonal variation decreased with age; cycle length variation decreased and then increased. Within individual women, cycle lengths were highly variable while hormone levels were more stable. Women differed more from each other in hormone levels than for cycle lengths. CONCLUSIONS: Aggregate-level analyses show general changes in steroid hormones and cycle length but cannot show variation within and across women. Individuals' cycle lengths were too variable to predict hormone levels. Clinicians should obtain more data on individual women's hormonal patterns when determining fertility or menopause treatments.

Validity of methods for analyzing urinary steroid data to detect ovulation in athletes.

PURPOSE: The purpose of this study was to determine whether the accuracy of ovulation detection algorithms is compromised when applied to menstrual cycles exhibiting subclinical hormonal abnormalities, which are particularly prevalent in female athletes. METHODS: The validity of five ovulation detection algorithms was compared between 25 regularly exercising women and 15 sedentary controls. Subjects collected daily urine samples for an entire menstrual cycle for analysis of estrone-3-glucuronide (E1G), pregnanediol-3-glucuronide (PDG), and luteinizing hormone (LH). The algorithms were applied to determine their sensitivity (% of true ovulatory cycles), specificity (% of true anovulatory cycles), and the deviation from the reference day of ovulation (difference scores). RESULTS: The sensitivity was > 80% in all algorithms except Baird's E1G/PDG ratio algorithm (74%) and Kassam's PDG ratio algorithm (78%). All algorithms, except Kassam's PDG ratio algorithm (80%), were found to exhibit specificities < 70%. Baird's E1G/PDG ratio algorithm was the most accurate in estimating the day of ovulation by deviating only -0.2 +/- 0.3 d from the reference day in the exercising female cycles and -0.5 +/- 0.3 d in the controls. No statistical differences in the sensitivities of the algorithms were found between the exercising and control cycles. When comparing the deviation from the reference day of ovulation between subject groups, no statistical difference was found. CONCLUSION: The algorithms display similar validity in determining the presence and day of ovulation between subject groups, and thus may be applied to cycles exhibiting subclinical hormonal abnormalities as commonly observed in exercising women.

Serum, plasma, and dried blood spot high-sensitivity C-reactive protein enzyme immunoassay for population research.

C-reactive protein (CRP) is used as a biomarker of morbidity and mortality risk in studies of population health, and is essential to interpretation of several micronutrient biomarkers. There is thus a need for a robust high-sensitivity CRP (hsCRP) measurement method for large-scale, non-clinical studies. We developed an efficient, inexpensive assay suitable for quantifying CRP across the physiological range using any blood specimen type. The ELISA uses readily available monoclonal antibodies to measure CRP in serum, plasma, or dried blood spots (DBS) made from venous or capillary blood. Assay performance was evaluated by standard methods, including comparison with a previously described assay. Effects of specimen type were tested by measuring CRP in 52 matched serum, plasma, and venous and capillary dried blood spot specimens. Long- and short-term CRP stability were evaluated. Assessments of assay limits of detection, linearity, recovery, imprecision, and concordance with an established method (Pearson correlation=0.988, n=20) demonstrated the validity of the new assay. CRP measurements in serum, plasma, and DBS had Pearson correlations from 0.974 to 0.995, n=52, but CRP in serum was on average 1.6 times (SD 0.37) higher than in DBS. CRP was stable in frozen serum for up to 34 months, but DBS CRP declined quickly with exposure to ambient temperatures, and across long-term storage at -20°C. This hsCRP assay is a robust and inexpensive tool designed for use in large-scale population health research. Our results indicate that DBS CRP is less stable than previously reported.

Assessment of the relative dose-response test based on serum retinol-binding protein instead of serum retinol in determining low hepatic vitamin A stores.

BACKGROUND: The relative dose-response (RDR) test, which measures the percentage of change in serum retinol concentration in response to an oral vitamin A (VA) dose, is a functional reference method to assess low hepatic VA stores. However, problems due to the relative instability of retinol, which is measured in the traditional RDR test, could be circumvented if retinol-binding protein (RBP), a more stable marker of VA, could be measured instead of retinol to provide the RDR value. OBJECTIVE: The objective was to compare classification of VA status assessed by retinol-RDR with that assessed by using RBP-RDR. DESIGN: With the use of serum samples from 57 lactating women in northern Kenya collected in August-September 2006, we assessed the accuracy of RBP-RDR in predicting low hepatic VA stores through receiver operator characteristic (ROC) analysis using retinol-RDR values as the gold standard. By using regression analysis, we explored the effects of 1) body mass index (BMI) on RBP-RDR performance and 2) the oral VA dose on the retinol-RBP molar ratio. RESULTS: The classificatory accuracy of RBP-RDR was low to moderate (n = 50; ROC area: 0.56-0.72) depending on the cutoffs used. RBP-RDR systematically overestimated VA deficiency with higher BMI, although it was superior to a single measurement of serum retinol. The discrepancy between RBP-RDR and retinol-RDR appears to originate in a retinol concentration-dependent alteration of the retinol-RBP molar ratio triggered by the oral dose. CONCLUSIONS: RBP-RDR has the potential to serve as a moderately accurate surrogate measure of retinol-RDR if the variation associated with BMI is understood and adjusted. Further studies should clarify the dynamics of the retinol-RBP molar ratio and its link to RBP-RDR performance.