OP17.08: Three methods of auditing the nuchal translucency component of a routine combined screening service

Abstract

Objectives:To determine whether the type of test used for trisomy 21 screening significantly alters the effect that nuchal translucency (NT) variability has on the result. Methods: Our case series included women who underwent aneuploidy screening at a single maternal fetal medicine practice from July 2004 through September 2009. The NT measurements used in each screen were altered to reflect discrepancies in measurement based on an analysis of our unit's average variation over a nine month period. This mean variation was derived by averaging 500 sets of 3 NT measurements from consecutive patients in our unit from January 2009 through September 2009. Results were then analyzed to identify subjects for whom the variance in NT measurement affected interpretation of risk according to unit cutoffs for each type of screen (1 : 230 for first-trimester and 1 : 110 for integrated). Descriptive and Pearson's chi-square statistics were used. Results: Of 13,633 total subjects, 6,314 had integrated screening, and 7,319 had first-trimester combined. Each screen's original NT measurement was re-calculated to reflect our unit's average variation (0.2 mm). The results were modeled based on a 0.4 mm total range to account for the possibility of an increase or decrease in measurement. The overall number of patients whose results were affected by a change in risk interpretation was 496 (6.8%) for first-trimester and 141 (2.2%) for integrated screening. A comparison of the overall number of subjects affected by each type of screen was statistically significant (P < 0.0001). Conclusions:The effect of variation in NT measurement can be minimized by using integrated screening as compared to firsttrimester combined. OP17.08Three methods of auditing the nuchal translucency component of a routine combined screening service Objectives: To assess three methods of auditing the nuchal translucency (NT) component of a routine combined screening service recently introduced into a UK hospital. To evaluate their impact on service quality. Methods: Data for all women requesting combined screening were collected for the first 6 months of the service. 3 separate NT images were measured. Measurement agreement of ±0.1 mm was required for the NT to be achieved. Audit 1 -percentage of NT achieved. Audit 2 -number of data sets, NT distributions (% below the mean) and bias were obtained from the national Down syndrome Screening Quality Assurance Support Service (DQASS). Audit 3-5 anonymised NT images were assessed independently by 2 sonographers according to FMF criteria. Audits 2 and 3 were scored as follows: 3 = good, 2 = safe, 1 = poor. 10 FMF accredited sonographers were audited over the 6 month period. Results:The results are shown in Table 1. Conclusions: The methods assess different but important components of combined screening. Individual sonographer scores differ across the three methods. Using a combination of the 3 methods provides both quantitative and qualitative audit of the service. In addition it offers a comprehensive evaluation of indiv...