v4.2.8

Update / Fix

Rephrase the age correction advice for CDC

v4.2.7

Update

Babies measured against CDC reference are not corrected for gestational age at 37 weeks and above, nor are they corrected for gestational age if born premature once they reach two years of age.

The update implements this rule and updates the advice strings for clinicians and lay members.

v4.2.6

Update

Fixes the lack of meaningful error if preterm calculations are requested in the CDC reference (where no reference data exists)

v4.2.5

Patch

Typo fix in BMI upper threshold critical to API functionality

v4.2.4

Update

Implements SDS cut offs to replace hard coded cut-offs

v4.2.3

Updates

Moves the midparental height calculations into the package and out of the server

Implements the regression to the mean concept (Wright et al.)

Adds tests

(skipping 4.2.2 due to versioning error on deploy)

v4.2.2

Updates

Moves the midparental height calculations into the package and out of the server

Implements the regression to the mean concept (Wright et al.)

Adds tests

v4.2.1

Update

Reverting previous change to create_chart - creates curves from all LMS values

v4.2.0

Update

• Trisomy 21 (AAP) reference added
• reorganisation of create_chart function - previously this would create centile lines by calculating a measurement for a given reference, measurement method, sex and z score at fixed decimal age intervals. This generated often uneven lines, particularly when growth velocity is quite steady. This update generates measurement for each interval in the data set meaning no interpolation between ages is necessary, making it quicker. It applies the default_youngest_reference flag more clearly, so that where references overlap and two values exist for a given age (eg at 2 y where infant are measured both lying and standing), a measurement for each is returned, allowing lines with clean breaks to be plotted with no gap. It also reduces the number of decimal places in the return object, again speeding things up.

NOTE: It is likely this latter change will break the tests for chart-coordinates in the server, so for the moment that is pinned to v4.1.1

NOTE: that although the T21 AAP reference has been added, there are no tests for this as there is currently no published gold standard - if anyone knows of one do please get in touch. The accuracy of results relating to this reference for the moment therefore cannot be guaranteed.

v4.1.1

Age bands

Since the introduction of CDC, which uses a different centile format collection, the centile band advice is nolonger accurate.
UK-WHO use 2/3 SDS intervals between centiles, so that the collection becomes 0.4th (-2.67SDS), 2nd (-2SDS), 9th (-1.33), 25th (-0.67), 50th (0 SDS), 75th, 91st, 98th, 99.6th - these are termed 'cole-nine-centiles' as a collection name for shorthand
CDC uses a mixture of centiles in their charts - standard is termed 'five-percent-centiles', comprising 5th, 10th, 25th, 50th, 75th, 90th, 95th. For depicting more extremes, 3rd centile is added and is termed 'three-percent-centiles'. The extended BMI release of 2022 included here recognised the significant impact of obesity on population health and sought to reflect this in the charting. It recognised the difficulties of using SDS at higher values discussed elsewhere and introduced a further parameter (sigma) in the LMS dataset, which defines dispersion or spread of all BMI measurements above the 95th centile (p95).
sigma = sqrt(2) * S * exp(L * (log(BMI/M) - log(P95/M)))
This has allowed the introduction of a new centile collection, termed 'eight-five-percent-centiles' which include all those in the five-percent-centiles with the additional 85th, 90th, 95th, 99.9th, 99.99th.

While this is all implemented for CDC in RCPCHGrowth, the centile_band is text for lay users to know how far the measurement is from the nearest centile. The Measurement class though cannot know what sort of chart it is being plotted on so the solution here is to produce advice based on the standard chart for reference and measurement_method.