Since 2000, Alpha has included NT features which have proved to be important and useful.  Alpha was the first screening software to introduce monitoring NT performance based on median MoM's, standard deviations and slope of NT in line with increasing gestational age.   These features help the user quantify and monitor NT measurements for individual sonographers and, where appropriate, allow for systematic measurement differences between sonographers.    The SURUSS study showed  that there was about a 5 percentage point increase in detection rate when sonographer specific medians were used compared to centre specific medians.  αlpha also provides the option of using sonographer-specific medians or centre specific medians.

1. αlpha  records the identity of the sonographer

αlpha allows the user to record the identity of the sonographer for each NT measurement on the data entry screen together with the other information required for the screening test on a patient. Click here to see how this is done.  

If the identified sonographer does not yet have NT median value assigned the centre specific sonographer medians will be used.  This may arise if the sonographer has not yet taken enough NT measurements to establish normal medians.  When the sonographer has taken enough NT measurements, normal medians can be established using the tabulation and regression features in αlpha (see below).

2. Sonographer-specific tabulations of NT measurements can be made

Sonographer-specific tabulations of NT measurements include an estimate of the standard deviation of NT MoM values which can be compared with published estimates. This gives an indication of whether the precision of NT measurement is as expected.  The tabulation also includes the median NT measurements and NT MoM in each CRL group, the overall median MoM value and the tenth and ninetieth centile. The median MoM should generally lie between  in the 95% confidence interval around 1.0 MoM.  The NT standard deviation (in log10 MoM) will be less than 0.18 and the NT slope will be between 15% and 25% increase per week.  Click here to see an example of a sonographer specific tabulation.  

3. Coefficients of the normal median NT equation can be derived from sonographer-specific regressions

Sonographer-specific regressions of NT according to crown rump length (CRL) measurement provide an indication of the rate of increase of the median NT with gestational age. Coefficients of the normal median NT equation can be specified for each sonographer.   αlpha automatically selects the appropriate coefficients for calculating the NT MoM, based on the sonographer code entered by the user. Click here to see an example of a sonographer-specific regression. 

4. Monitoring NT medians

αlpha includes a facility which provides quick and easy monitoring of sonographer or centre specific nuchal translucency medians.   This will be useful for users who need to regularly monitor NT medians for a large group of sonographers.     A sonographer can be selected from a list and a graph showing the measurements is immediately shown together with the number of scans performed, median MoM NT value, standard deviation and percentage increase per week.  Click here to see an example.