Maternal blood levels of human placental lactogen in the prediction of fetal growth retardation: choosing a cut‐off point between normal and abnormal

Abstract

Single estimations of serum human placental lactogen (hPL) were made in 527 unselected women between 36 and 40 weeks gestation. The association between decreased serum levels of hPL and intrauterine growth retardation was confirmed. The effect of changing the cut-off point between normality and abnormality on the sensitivity, specificity and predictive value was determined. When the 10th centile of hPL values was used, 29% of all growth-retarded fetuses were identified apd 91% of all 'normal' fetuses were excluded. The 15th and 25th centiles yielded improved sensitivities of 37 and 50% respectively, but specificity was reduced. It is suggested that the 10th centile provides a good compromise between sensitivity on the one hand and specificity and predictive value on the other.

Human placental lactogen in pre‐eclampsia

“…Whereas for most of the population the appropriate figure (i.e. the 10th centile; Lilford et al 1983) is 5 mg/l, in this particular subgroup the figure is 5 . 6 mg/l.…”

“…Data were analysed by calculation of means and standard deviations after logarithmic transformation of values; the latter was used for comparison of subpopulations by Student's t-test. Data were also ranked and divided into centiles for analysis of sensitivity, predictive value and specificity (Chard & Klopper 1982), using the 10th centile of the relevant group as the cut-off point between normal and abnormal (Lilford et al 1983).…”

An audit of the detection and management of small‐for‐gestational age babies

“…In spite of a continued concern with diagnostic techniques (Lilford et al 1983;Dornan et al 1984), the efficiency of detection remains disappointing. Biochemical screening methods (Aickin er al.…”

Hormones of the Placenta: hCG and hPL

“…The sensitivity of the test (proportion of positive results in patients with the abnormality) ranges from 29 to SO% depending upon the chosen cut-off point between normal and abnormal (Lilford et al, 1983). Serial levels have better predictive value than isolated levels .…”