Congenital Z-Scores

Introduction

Z-scores are frequently used in congenital echocardiography and fetal echocardiography to express the deviation of a measurement from the size-specific or age-specific mean of a population, as a way to account for changes in growth or age when reporting normal values. You can also use z-scores to provide a means of determining the degree to which a measurement deviates from the expected norms, by indicating how many standard deviations above or below a size- or age-specific population mean a measurement falls.

Congenital Echocardiography Support

The Clinical Reporting Application (CRA) supports congenital echocardiography and fetal echocardiography reporting of z-scores and their associated values for some measured values. For a list of measurements that support the calculation of this data, see Z-Score Tables for additional information.

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Age Bracket Determination

In reporting z-scores, CRA first attempts to determine the age bracket (adult, congenital, or fetal) into which the study falls. The parameters used in this determination include:

  • Age and Body Surface Area (BSA) for congenital studies
  • LMP or EDC for fetal studies (determination of gestational age)

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Congenital Cutoff Age

By default, a calculated patient age that is less than 21 years is considered to be a congenital study. Similarly, the system can be configured to include or exclude BSA in the determination of whether or not a study is a congenital study. By default, BSA is not used in this determination.

Note:

The congenital cutoff age is site configured. See your System Administrator for more information.

The parameters used to calculate congenital z-scores and associated regression data vary with system configuration.

The regression data calculated by CRA includes z-score, percentile, normal range, and the regression mean.

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Displaying Z-Score Values

Introduction

Measurement controls with a z-score configuration have a different appearance than standard measurement controls.  

The following table describes the information that Synapse displays in a report:

Field

Description

Name
  • Represents individual measurement or calculation names within a measurement control.

Value
  • Represents a measurement or calculation value.
  • To enter a new value, select the existing value and enter a new value in the Value field.

Prior
  • Represents a measurement or calculation value from a previous study.
  • The Prior column header displays the date of the previous study.
  • Trends indicates prior values exist and is enabled when at least two values from two different studies are known; otherwise, it is disabled.
  • When enabled, click Trends to view a graph with both the prior and current measurements.
  • Fetal Z-Scores will only trend on the current pregnancy.

Normal
  • Represents a dynamically generated normal range based on z-score instead of a static normal range for a measurement.
  • Values that are outside of the normal range display in red.

Z-Score
  • The number of standard deviations from the mean.
  • The calculated z-score value for a measurement based on the selected instance of its value.
  • When a z-score cannot be calculated for a measurement, N/A displays in the z-score field.  
  • Hover over the z-score field to view a tooltip indicating why the z-score could not be calculated.

Prior Z-Score
  • A previous study z-score.

Mean (Optional)
  • The mean value is the average value of a measurement or calculation for similar patients.

Percentile (Optional)
  • The percentile of the z-score.

Instance Selector
  • When multiple instances exist, the Instance Selector is represented by the icon on the right side of the measurement chart.
  • Use as an on/off toggle. 

If any of the independent variables for a measurement are edited, the calculated z-score and associated data are updated. Similarly, if an independent variable for this measurement is deleted, the associated regression data cannot be calculated.

When multiple instances exist and all of the criteria for the required study type have been met, z-scores and their associated data are determined for every instance of a measurement that supports this calculation. The calculated values and associated normals, z-score, and percentile are only seen in the measurement control for the selected value. If you select a different instance of the value, the associated regression data is updated.

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Related Topics

Working with Measurement Controls

Keyboard Shortcuts for Clinical Reporting Application

Z-Score Tables