Quality Assessment of Fetal Nuchal Translucency Measurements in the First Trimester of Pregnancy

Abstract

Objectives: To evaluate and compare the performance of various quality control methods for nuchal translucency (NT) measurements. Methods: Fetal NT measurements performed over a oneyear period in a single center were used for the study. The retrospective quality review methods proposed by the Fetal Medicine Foundation (FMF) and the Woman & Infants Hospital of Rhode Island (WIHRI) were assessed in the whole dataset and in sonographer-specific distributions. Further prospective statistic process control (SPC) methods were applied (Shewhart x and s charts, exponentially weighted moving average (EWMA) and cumulative sum (CUSUM) charts). Results: Three thousand five hundred and seventy eight NT measurements obtained by seven sonographers were eligible for designed analysis. In the assessment of the sonographer-specific NT distributions three of them did not meet due to the underestimation the FMF and one the WIHRI criteria. Using SPC methods, three sonographers presented unsatisfactory performance with underestimation, three sonographers overall satisfactory performance with transient periods of over-and underestimation and one sonographer showed perfect performance. MUDr. Martin HynekConclusions: Assessed SPC methods showed close agreement with the retrospective ones, but with the advantage that they can be applied prospectively allowing the prompt action in case of malperformace. The EWMA and CUSUM methods were regarded as the most suitable.

Exponentially weighted moving average chart as a suitable tool for nuchal translucency quality review

“…suggested a delta‐based approach, Sabria et al . presented a MoM‐based one and others have reported a valuable contribution of CUSUM to prospective NT quality control . However, the main disadvantage we have observed is that CUSUM, because of its elephant‐like memory, lacks the ability to return rapidly to within the control limits after the out‐of‐control process is rectified.…”

“…The CUSUM method has the benefits of a simple formulation and very intuitive graphical presentation of two curves: an upper curve that monitors overestimation and a lower curve that monitors underestimation. It is a sensitive method that can quickly detect changes in quality (reported values of out‐of‐control ARL of 34 and MDRL of 60 and 28) . Biau et al .…”

“…Second, our previously described MoM‐based CUSUM model was applied to each sonographer using the decision interval h = ±10 and the size of the shift we desired to detect, δ = 0.5693.…”

“…in 2011 were the first to propose its use for NT quality review, using NT deviation in millimetres. Subsequently, others have designed and successfully applied MoM‐based CUSUM charts …”