A single cervical fetal fibronectin screening test in a population at low risk for preterm delivery: an improvement on clinical indicators?

OBJECTIVE

To assess the accuracy of a single cervical fetal fibronectin test to predict spontaneous preterm delivery in an unselected antenatal population.

DESIGN

A prospective blind cohort study.

SETTING

Antenatal clinic of a teaching hospital in a Brussels semiurban area.

PARTICIPANTS

An unselected group of 170 women followed at the antenatal clinic.

METHODS

A single cervical sample was obtained between 24 and 33 completed weeks of pregnancy. The fibronectin test was compared with clinical evaluation and their predictive properties were assessed.

RESULTS

Fifteen women were excluded from the analysis because of elective preterm delivery for medical indications or loss to follow up. Of the 155 remaining women, nine (7%) had a spontaneous preterm delivery. For a single fetal fibronectin test, the sensitivity was 26.7%, the specificity 95.7%, and the positive and negative predictive values 40.0% and 92.4%, respectively. The likelihood ratio of a positive was similar to that of clinical predictors of preterm birth (LR = 6.2; 95% CI 2.0-19.6). Sensitivities were low for both clinical criteria and the fetal fibronectin test.

CONCLUSIONS

Because of low sensitivity in a low risk population, screening for preterm delivery should not be based on the result of a single fetal fibronectin test alone. However, due to its high specificity the test might be useful in avoiding unnecessary medical intervention.

Inhibitory action of androstenedione on the proliferation and cell cycle kinetics of aromatase-free MXT and MCF-7 mammary tumour cell lines

The effects of androstenedione (AD) on cell proliferation and kinetics have been measured in MXT mouse and MCF-7 human mammary cancer cell lines using SAMBA 200 cell image analysis of Feulgen-stained nuclei. At a concentration of 0.01 microM AD inhibited the proliferation of both cell lines whereas a higher dose (1 microM) was inhibitory on MCF-7 cell proliferation but stimulatory in MXT cells. It is unlikely that these effects are due to aromization of AD into oestrogen since (a) both cell lines were devoid of aromatase and (b) both cell lines were similarly affected by oestradiol (E2), being stimulated at low concentrations and inhibited at high doses. Furthermore, inhibition by AD seems to occur, at least in part, by blockade of the cell cycle whereas that by E2 appears to be cell cycle independent.

Myometrial beta 1-adrenoreceptors are detectable only in the midfollicular phase

Both alpha- and beta-adrenergic receptors have been identified in human myometrium by radioligand binding. Both types of receptors mediate uterine contractility: alpha-adrenergic agonists cause uterine contraction, whereas beta-adrenergic agonists induce relaxation. We studied the possible regulatory effects of gonadal steroids on the affinity, concentration, subtype distribution, and linkage to adenylate cyclase of beta-adrenergic receptors in human myometrium removed during different phases of the menstrual cycle, from postmenopausal women and during depo-progestin (medroxyprogesterone acetate) therapy. We identified beta-adrenergic receptors in human myometrial membranes using the radiolabeled antagonist (--)-[3H]-dihydroalprenolol (DHA). The binding of this radioligand was rapid, reversible, of high affinity (KD = 0.71 nM) and stereo-selective. Total beta-receptor concentration was determined by Scatchard analysis of DHA saturation binding and the ratio of receptor subtypes determined by computer-assisted analysis of beta 2 selective antagonist ICI 118 551/DHA competition binding curves. The fraction of receptors functionally coupled to adenylate cyclase was determined by the agonist/N-ethylmaleimide inactivation method. The affinity of DHA and the fraction of receptors undergoing functional coupling was similar under all hormonal conditions. However, whereas the net concentration of beta-receptors was the same in all groups, beta 1-adrenoreceptors could only be detected in myometrial particulate fractions from uteri obtained in the midfollicular phase, indicating the importance of considering adrenoreceptor subtypes as separately regulatable receptors.

Differential regulation of alpha-adrenergic receptor subclasses by gonadal steroids in human myometrium

Adrenergic receptors have been shown to be involved in uterine contractility. alpha-Adrenergic receptors cause uterine contraction, whereas beta-adrenergic receptors induce relaxation. In animals, myometrial alpha-adrenergic receptors are regulated by gonadal steroids. We have identified alpha 1- and alpha 2-adrenergic receptors in myometrial membranes using the newly developed radiolabeled specific antagonists [3H]prazosin and [3H]rauwolscine. This allowed characterization of both receptor subclasses individually and study of them in various physiological and pharmacological conditions in the human, i.e. during different phases of the menstrual cycle, in postmenopausal women, term pregnancy, and during depo-progestin (medroxyprogesterone acetate) therapy. The affinity and number of alpha 1-adrenergic receptors were unchanged in all conditions, whereas the number of alpha 2-adrenergic receptors increased concomitantly with circulating plasma estradiol levels. However, this latter effect was counteracted by progesterone. These results are an example of the heteroregulation of membrane receptors by estrogens and progesterone and throw new light on the regulatory mechanisms involved in uterine contractility in the human.

Identification and characterization of alpha 2-adrenergic receptors in human myometrium by [3H]rauwolscine binding

Human myometrium contains alpha 3-adrenergic receptors which can be identified by binding of the alpha 2-adrenergic antagonist [3H]rauwolscine. Scatchard analysis of saturation binding data on myometrial membranes revealed that [3H]rauwolscine bound to a single class of noncooperative sites (262 +/- 89 fmol/mg of membrane protein) with high affinity (i.e., with an equilibrium dissociation constant of 5.3 +/- 2.2 nM). The alpha 2-adrenergic nature of these sites was derived from the order of potencies and stereospecificity of alpha-adrenergic agonists and antagonists to compete with [3H]rauwolscine binding.