Precision and long-term stability of different estradiol immunoassays assessed in a multi-center quality control study.

BACKGROUND: Because of the vast range of physiological relevant estradiol concentrations the requirements to be met by an estradiol assay are high. In the present study the performance of various commercially available estradiol assays was evaluated with regard to imprecision and long-term stability. METHODS: Precision and long-term stability of 7 commercially available estradiol immunoassays were assessed in a multi-centre quality control study based on the repeated measurement of liquid BIOREF estradiol control sera by 18 laboratories during a 14-month study period. RESULTS: The mean estradiol concentrations determined in 594 runs performed for each control level were 71 pg/ml, 349 pg/ml and 676 pg/ml. A high variation was found for the method specific mean values calculated from all results measured with the same method, which ranged between 32 - 90 pg/ml, 187 - 392 pg/ml and 373 - 790 pg/ml, resulting in a similar high inter-laboratory variation with coefficients of variation (CVs) of 25.0%, 16.7% and 17.5%. In contrast, the intra-laboratory variation of estradiol values as well as the variation of values measured with the same method were found to be considerably lower with coefficients of variation < 10% for most laboratories and methods; only the low control level was measured with CV values > 10% by the majority of laboratories and methods. For none of the laboratories a tendency was observed in the results from beginning to end of the 14 month study period indicating a high uniformity in assay production and a good long-term stability of the control material used. CONCLUSIONS: The present data demonstrate that also with the currently available estradiol immunoassays the comparability of results measured with different methods is limited. With most assays very low estradiol concentrations, as observed in postmenopausal women, can be determined only with a precision which is not adequate for clinical assessment.

Multicentre evaluation of performance of C-reactive protein analysis over a one-year period.

This communication deals with a longitudinal evaluation of C-reactive protein (CRP) analysis during a one-year period using a single lot of liquid control sera (3 levels) (BIOREF-CRP levels 1, 2 and 3) in different laboratories. A total of 652 sets of data were returned from 20 participating laboratories using 13 different reagent-measuring device combinations. The use of the control materials was defined in a standard operating procedure. Data was returned to the organizers on a monthly basis and questions could be asked or problems presented during the evaluation period. Although the performance of different reagents varied, the control materials were shown to be stable over the whole of the evaluation period when stored at 4-7 degrees C in a refrigerator/cold room. Typical problems were encountered, examples of which are presented here in graphical and tabular form.

Corticotropin-releasing hormone decreases feeding, oxygen consumption and activity of genetically obese (ob/ob) and lean mice.

Acute effects of intracerebroventricularly administered corticotropin-releasing hormone (CRH) on deprivation-induced food intake, whole-body oxygen consumption, brown adipose tissue metabolism, and several locomotive behaviors were examined in 6- to 7-wk-old female genetically obese (ob/ob) and lean mice. Corticotropin-releasing hormone depressed food intake in a dose-dependent manner, with a tendency for greater suppression of intake in intact ob/ob mice than in lean mice. Adrenalectomy abolished this tendency for CRH to be more potent in ob/ob mice than in lean mice. Corticotropin-releasing hormone also lowered the oxygen consumption of ob/ob and lean mice, without affecting brown adipose tissue metabolism as assessed by measurement of GDP binding to brown adipose tissue mitochondria. Grooming activity was lowered in CRH-injected mice. The CRH-induced lowering of oxygen consumption and grooming activity in mice contrasts with CRH-induced elevations of oxygen consumption and grooming in rats, suggesting species-specific responses to this peptide. Because effects of CRH were similar in adrenalectomized ob/ob and lean mice, it is unlikely that obesity-producing abnormalities in ob/ob mice are related to abnormal CRH action mechanisms. However, potential abnormalities in CRH synthesis and/or release cannot be excluded.

[Iron resorption and the effects of iron supplementation in blood donors]. / Untersuchungen zur Eisen-Resorption und des Effektes der Eisen-Supplementierung bei Blutspendern.

Topical values for some haematological factors such as Hb and Ery as well as transferrin and ferritin were determined in 7 female blood donors and 8 male blood donors during the years of their work as blood donors. Subsequently, an iron resorption test was carried out which unexpectedly resulted in low rates of resorption ranging from 5.6% in men to 3.7% in women. After supplementing with vitaferro for 3 months the ferritin values which initially lay around the lower limiting value of 20 or 10 mg/l in men or women had doubled.

Rumination syndrome in children treated by increased holding.

Rumination syndrome--the frequent regurgitation of previously ingested food into the mouth where it is chewed--is a common, life-threatening disorder of retarded individuals. Four cases are described in which holding a retarded, ruminating child for 10-15 min before, during, and after meals, was associated with remission of rumination. Simple holding was effective in three; in the fourth, it was necessary to punish the child by putting her into a separate room for 3 min immediately after regurgitation. A within-subject reversal experimental design suggested that holding and not simple distraction was the effective component of the treatment. Treatment benefits were well maintained when the child returned to a home environment in which he or she continued to be held periodically. It is proposed that there are two behavioral etiologies for idiopathic rumination syndrome--social deprivation and reward learning through increased attention for regurgitation. Holding is the treatment of choice for the first type, and punishment with time out may be necessary to suppress regurgitation in the second type.

Heart rate response to touch.

The effect of tactile stimulation on heart rate (HR) in humans was investigated under three conditions: 1) Experimenter outside of room in which subject is sitting; 2) experimenter in the room with the subject; 3) experimenter in the room while touching the subject's right wrist. Nonsignificant increases in HR were observed when the experimenter entered the room (X = 0.64 beats per minute (bpm)). Conversely, large decreases occurred when the experimenter placed his hand on the subject's wrist (X = 9.16 bpm, p is less than 0.05). To determine if tactile stimulation alone accounts for these differences three comparisons were made in a second experiment: 1) Experimenter out of test room, subject touches own wrist; 2) experimenter in room standing near subject; 3) experimenter touching subject's wrist. Subjects showed slightly elevated HR during the self-touch condition (X = 1.26 bpm, not significant). Although no change was noted with the experimenter standing beside the subject, there were decreases, as in Experiment I, when the experimenter touched the subject's wrist (X = 1.75 bpm, p is less than 0.05). These results suggest that the observed decreases in HR were contingent upon another person's touch. While self-tactile stimulation produced a slight increase in HR, tactile stimulation by another caused bradycardia.

Realtion of heart rate control to heartbeat perception.

The relation of heartbeat perception to voluntary control of heart rate (HR) and to learning of enhanced HR control during feedback was studied in three experiments. In Experiment I heartbeat perception was unrelated to voluntary control of HR but was negatively correlated with HR learning. Experiments II and III showed that heartbeat perception was unrelated to either initial voluntary control or learning and suggested that sampling error accounted for the negative correlation in Experiment I. Experiment I also demonstrated that learned increases in HR are retained for at least 10 weeks following feedback training. Autonomic Perception Questionnaire scores were not predictive of voluntary HR control or learning.