Abstract

GRANDI, Carlos. Estimación del acuerdo entre dos métodos para medición clínica de la edad gestacional. Arch. argent. pediatr. [online]. 2006, vol.104, n.2, pp.114-119. ISSN 0325-0075.

Introduction. In the clinical practice, a new method frequently can only be assessed by means of its comparison against other established techniques (gold standard). The objective of the present work was to describe an approach -through graphical techniques and simple statistical calculations- to assess the agreement level between two methods for clinical measurement of gestational age and to determine if they are interchangeable. Population, material and methods. This is an observational cohort study. Between 2000 and 2001, 137 pregnant women were prospectively enrolled at the Hospital Materno-Infantil Ramón Sardá of Buenos Aires before the 16^th week of gestation. The last normal menstrual period and ultrasound scan measurements were used for estimating gestational age. Mean difference, standard deviation and 95% confidence interval (limits of agreement) between the methods, and the mean of the two measurements were calculated and plotted for each case. Results. Mean gestational age at the first ultrasound scan was 19.6 (SD 4.9; 95% CI 18.7-20.4) weeks. The agreement between both methods were 71.5% (95% CI 63-78) ± 10 weeks and 82.5% (95% CI 75-87) ± 2 weeks. Mean difference was 0.35 + 1.89 (95% CI 0.03-0.67) weeks and the limits of agreement showed that, independently of gestational age, differences reached 7.5 weeks. Conclusions. The estimation of gestational age by the last normal menstrual period overestimated the one estimated ultrasound scan ("gold standard") by 25% and underestimated it by 20%. In the clinical practice both methods are not interchangeable.

Keywords : Gestational age; Ultrasound; Agreement.

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