Rapid fetal fibronectin testing to predict preterm birth in women with symptoms of premature labour: a systematic review and cost analysis

BACKGROUND

Premature birth is defined as birth of before 37 completed weeks' gestation. Not all pregnant women showing symptoms of preterm labour will go on to deliver before 37 weeks' gestation. Hence, addition of fetal fibronectin (fFN) testing to the diagnostic workup of women with suspected preterm labour may help to identify those women who do not require active management, and thus avoid unnecessary interventions, hospitalisations and associated costs.

OBJECTIVE

To assess the clinical effectiveness and cost-effectiveness of rapid fFN testing in predicting preterm birth (PTB) in symptomatic women.

DATA SOURCES

Bibliographic databases (including EMBASE, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials) were searched from 2000 to September/November 2011. Trial registers were also searched.

REVIEW METHODS

Systematic review methods followed published guidance; we assessed clinical effectiveness and updated a previous systematic review of test accuracy. Risk of bias was assessed using the Cochrane tool (randomised controlled trials; RCTs) and a modification of QUADAS-2 (diagnostic test accuracy studies; DTAs). Summary risk ratios or weighted mean difference were calculated using random-effects models. Summary sensitivity and specificity used a bivariate summary receiver operating characteristic model. Heterogeneity was investigated using subgroup and sensitivity analyses. Health economic analysis focused on cost consequences. The time horizon was hospital admission for observation. A main structural assumption was that, compared with usual care, fFN testing doesn't increase adverse events or negative pregnancy outcomes.

RESULTS

Five RCTs and 15 new DTAs were identified. No RCT reported significant effects of fFN testing on maternal or neonatal outcomes. One study reported a subgroup analysis of women with negative fFN test observed > 6 hours, which showed a reduction in length of hospital stay where results were known to clinicians. Combining data from new studies and the previous systematic review, the pooled estimates of sensitivity and specificity were: 76.7% and 82.7% for delivery within 7-10 days of testing; 69.1% and 84.4% for delivery < 34 weeks' gestation; and 60.8% and 82.3% for delivery < 37 weeks' gestation. Estimates were similar across all subgroups sensitivity analyses. The base-case cost analysis resulted in a cost saving of £23.87 for fFN testing compared with usual care. The fFN testing was cost-neutral at an approximate cost of £45. Probabilistic sensitivity analysis gave an incremental cost (saving) of -£25.59 (97.5% confidence interval -£304.96 to £240.06), indicating substantial uncertainty. Sensitivity analyses indicated that admission rate had the largest impact on results.

CONCLUSIONS

Fetal fibronectin testing has moderate accuracy for predicting PTB. The main potential role is likely to be reducing health-care resource usage by identifying women not requiring intervention. Evidence from RCTs suggests that fFN does not increase adverse outcomes and may reduce resource use. The base-case analysis showed a modest cost difference in favour of fFN testing, which is largely dependent on whether or not fFN testing reduces hospital admission. Currently, there are no high-quality studies and the existing trials were generally underpowered. Hence, there is a need for high-quality adequately powered trials using appropriate study designs to confirm the findings presented.

STUDY REGISTRATION

PROSPERO 2011:CRD42011001468. Available from www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42011001468.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The combined pituitary function test in children: an evaluation of the clinical usefulness of TRH and LHRH stimulation tests through a retrospective analysis of one hundred and twenty six cases

OBJECTIVE

The combined pituitary function test is routinely used in the endocrine investigation of short children. The TRH and luteinising hormone-releasing hormone (LHRH) response tests have been shown to be of minimal value in adults. We have evaluated the clinical utility of these tests in the context of combined pituitary function testing in children.

DESIGN

A retrospective analysis of basal hormone measurements and pituitary stimulation tests in relation to clinical assessment of pituitary function.

PATIENTS

One hundred and twenty-six children, 82 boys and 44 girls, aged 2-17 years, who had undergone pituitary function testing were studied.

RESULTS

The TSH response to TRH stimulation correlated directly with basal plasma TSH but not basal plasma total T4. In patients with an impaired response to stimulation, basal TSH concentrations were <2.0 mIU/l and significantly lower than in patients with a normal response (P < 0.0001). An impaired response to TRH stimulation had a positive predictive value of 0.43 and a negative predictive value of 0.90 for the diagnosis of hypopituitarism. A basal TSH concentration of <2.0 mIU/l had a positive predictive value of 0.22 and a negative predictive value of 0.92. A low basal T4 (normal range 60-140 nmol/l) in combination with an inappropriately low or normal basal TSH was always associated with a diagnosis of hypopituitarism. The responses of plasma LH and FSH to LHRH stimulation correlated directly with basal plasma LH and FSH concentrations. Basal gonadotrophin concentrations, basal sex hormone concentrations or response to LHRH stimulation could not distinguish patients with constitutional delay of growth and puberty from those with hypopituitarism. There was no apparent relationship between either basal gonadotrophin concentrations or response to LHRH stimulation and clinical assessment of pituitary function. In patients > or =13 years with constitutional delay of growth and puberty the median and interquartile ranges of basal LH and FSH were 1.4 IU/l (0.7-3.6) and 2.6 IU/l (2.2-5.2) respectively. The three hypopituitary patients in this study with chronological age > or =13 years had undetectable concentrations of both gonadotrophins. The response of LH and FSH to LHRH stimulation was significantly lower in patients > or =13 years with clinical hypopituitarism than in those with intact pituitary function (P <0.02).

CONCLUSION

TRH and LHRH tests in children with short stature appear to have little value over and above the baseline hormone measurements. An abnormal response to hormone stimulation is not diagnostic of hypothalamic-pituitary disease. We have demonstrated that neither TRH nor LHRH stimulation tests should be routinely used in the investigation of children with short stature.

Methylglyoxal-modified arginine residues--a signal for receptor-mediated endocytosis and degradation of proteins by monocytic THP-1 cells

Non-enzymatic glycosylation or glycation of proteins to form advanced glycation endproducts (AGE) has been proposed as a process which provides a signal for the degradation of proteins. Despite this, the AGE which act a recognition factor for receptor-mediated endocytosis and degradation of glycated proteins by monocytes and macrophages has not been identified. Methylglyoxal, a reactive alpha-oxoaldehyde and physiological metabolite, reacted irreversibly with arginine residues in proteins to form Ndelta-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine and Ndelta-(5-methyl-4-imidazolon-2-yl)ornithine residues. Human serum albumin minimally-modified with methylglyoxal (MG(min)-HSA) was bound by cell surface receptors of human monocytic THP-1 cells in vitro at 4 degrees C: the binding constant K(d) value was 377 +/- 35 nM and the number of receptors per cell was 5.9 +/- 0.2 X 10(5) (n = 12). N alpha-Acetyl-Ndelta-(5-hydro-5-methyl-4-imidazolon-2-yl)orni thine displaced MG(min)-HSA from THP-1 cells, suggesting that the Ndelta-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine residue was the receptor recognition factor. At 37 degrees C, MG(min)-HSA was internalised by THP-1 cells and degraded. Similar binding and degradation of human serum albumin modified by glucose-derived AGE was found but only when highly modified. MG(min)-HSA, therefore, is the first example of a protein minimally-modified by AGE-like compounds that binds specifically to monocyte receptors. The irreversible modification of proteins by methylglyoxal is a potent signal for the degradation of proteins by monocytic cells in which the arginine derivative, Ndelta-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine, is the receptor recognition factor. This factor is not present in glucose-modified proteins.

Synthesis and secretion of macrophage colony stimulating factor by mature human monocytes and human monocytic THP-1 cells induced by human serum albumin derivatives modified with methylglyoxal and glucose-derived advanced glycation endproducts

Human serum albumin minimally-modified by methylglyoxal (MGmin-HSA) stimulated the synthesis and secretion of macrophage-colony stimulating factor (M-CSF) by mature human monocytes in vitro. Human serum albumin minimally-modified by glucose-derived advanced glycation endproducts (AGEmin-HSA) and human serum albumin highly-modified by glucose-derived advanced glycation endproducts (AGE-HSA) stimulated much lower secretion of M-CSF from human monocytes than did MGmin-HSA. MGmin-HSA and AGE-HSA but not AGEmin-HSA also stimulated the growth of human monocytic THP-1 cells in vitro which was inhibited by polyclonal antibodies to human M-CSF. For MGmin-HSA, the median growth stimulatory concentration EC50 value was 0.24 +/- 0.07 microM and the maximal increase in cell growth was 36% of control cell growth (n = 24). Similar induction of secretion of M-CSF from monocytes in vivo may contribute to atherosclerosis in macro- and micro-angiopathy, particularly in the development of diabetic complications.

Induction of synthesis and secretion of interleukin 1 beta in the human monocytic THP-1 cells by human serum albumins modified with methylglyoxal and advanced glycation endproducts

Human serum albumin modified with 1-2 methylglyoxal residues per molecule of protein (MGmin-HSA) stimulated the synthesis and secretion of interleukin 1 beta (IL-1 beta) from human monocytic THP-1 cells in vitro. It was a more potent inducer of IL-1 beta synthesis than human serum albumin highly-modified with glucose-derived advanced glycation endproducts (AGE-HSA). With 20 microM ligand. IL-1 beta synthesis was (pg/10(6) cells): MGmin-HSA 484.5 +/- 50.3; AGE-HSA 30.6 +/- 2.0 (n = 3). IL-1 beta synthesis increased markedly with MGmin-HSA concentrations > 5 microM. IL-1 beta synthesis and secretion from monocytes in response to methylglyoxal-modified proteins in vivo may contribute to the development of macro- and micro-angiopathy, particularly in diabetes mellitus.

Molecular characteristics of methylglyoxal-modified bovine and human serum albumins. Comparison with glucose-derived advanced glycation endproduct-modified serum albumins

The amino acid modification, gel filtration chromatographic, and electrophoretic characteristics of bovine and human serum albumins irreversibly modified by methylglyoxal (MG-SA) and by glucose-derived advanced glycation endproducts (AGE-SA) were investigated. Methylglyoxal selectively modified arginine residues at low concentration (1 mM); at high methylglyoxal concentration (100 mM), the extent of arginine modification increased and lysine residues were also modified. Both arginine and lysine residues were modified in AGE-SA. Analytical gel filtration HPLC of serum albumin derivatives suggested that the proportion of dimers and oligomers increased with modification in both low and highly modified MG-SA and AGE-SA derivatives relative to unmodified serum albumins. In SDS-PAGE analysis, dimers and oligomers of low-modified MG-SA were dissociated into monomers, but not in highly modified MG-SA. MG-SA had increased anodic electrophoretic mobility under nondenaturing conditions at pH 8.6, indicating an increased net negative charge, which increased with extent of modification; highly modified MG-SA and AGE-SA had similar high electrophoretic mobilities. MG-SA derivatives were fluorescent: the fluorescence was characteristic of the arginine-derived imidazolone N delta-(5-methyl-4-imidazolon-2-yl)ornithine, but other fluorophores were also present. AGE-SA had similar fluorescence, attributed, in part, to glucose-derived imidazolones. AGE formed from glucose-modified proteins and AGE-like compounds formed from methylglyoxal-modified proteins may both be signals for recognition and degradation of senescent macromolecules.

Binding and modification of proteins by methylglyoxal under physiological conditions. A kinetic and mechanistic study with N alpha-acetylarginine, N alpha-acetylcysteine, and N alpha-acetyllysine, and bovine serum albumin

The physiological alpha-oxoaldehyde methylglyoxal binds and modifies arginine, lysine, and cysteine residues in proteins. The kinetics and mechanism of these reactions were investigated with N alpha-acetylamino acids and bovine serum albumin at pH 7.4 and 37 degrees C. The reaction of methylglyoxal with N alpha-acetylarginine involved the initial reversible formation of glycosylamine and 4,5-dihydroxy-5-methylimidazolidine derivatives, with further slow irreversible conversion to an imidazolone, N alpha-acetyl-N delta- (5-methyl-4-imidazolon-2-yl)ornithine. The imidazolone was fluorescent with an excitation lambda max value of 320 nm and an emission lambda max value of 398 nm. Methylglyoxal reacted reversibly with N alpha-acetyllysine to form glycosylamine and bisglycosylamine derivatives. Further reaction of these glycosylamines occurred to form brown, fluorescent oligomers that were not characterized. Methylglyoxal reacted rapidly and reversibly with N alpha-acetylcysteine to form the hemithioacetal adduct. The reaction of methylglyoxal with bovine serum albumin (BSA) at pH 7.4 and 37 degrees C involved the reversible and irreversible formation of methylglyoxal-BSA adducts. Irreversible modification of BSA occurred mainly on arginine residues to form imidazolone. The formation of methylglyoxal-modified proteins involves glycoxidation leading to advanced glycation end product-like fluorescence. It is expected to be increased in diabetes mellitus and may be linked to the development of diabetic complications.

Receptor-mediated endocytic uptake of methylglyoxal-modified serum albumin. Competition with advanced glycation end product-modified serum albumin at the advanced glycation end product receptor

Methylglyoxal binds and irreversibly modifies arginine and lysine residues in bovine serum albumin (BSA) under physiological conditions, producing a protein with an increased net negative charge at physiological pH. At 4 degrees C, methylglyoxal-modified BSA (MG-BSA) was bound by cell surface receptors on murine P388D1 macrophages. The apparent dissociation constant KD value was 435 +/- 2 nM, and there were 8.89 +/- 0.02 x 10(5) receptors/cell (n = 6), compare with an apparent KD value of 263 +/- 52 nM and 10.17 +/- 0.93 x 10(5) receptors/cell (n = 11) for advanced glycation end product-modified BSA (AGE-BSA). AGE-BSA competed with MG-BSA for binding to a common receptor; however, a component of AGE-BSA receptor binding could not be displaced by MG-BSA, and a component of MG-BSA receptor binding could not be displaced by AGE-BSA, suggesting that there are binding sites for both AGE-BSA and MG-BSA, competitive and noncompetitive, to MG-BSA and AGE-BSA on P388D1 cells at 4 degrees C. At 37 degrees C, receptor binding of AGE-BSA and MG-BSA was followed by endocytosis and lysosomal degradation of the modified protein. Methylglyoxal-modified proteins are ligands for the AGE receptor, and their formation and metabolism may be linked to the development of diabetic complications.