FHIR Chat · Quantity.value precision

Stream: implementers

Topic: Quantity.value precision

Anand Mohan Tumuluri (Jul 12 2016 at 17:36):

Are servers required to preserve insignificant decimal digits (e.g. 185.00 or 65.0) in Quantity.value while storing observations or medications? Or is it acceptable to ignore insignificant decimals and make them as 185 or 65?
The Quantity datatype has this statement but I am not able to clearly interpret it.
"The value contains the numerical value of the quantity, including an implicit precision"

Grahame Grieve (Jul 12 2016 at 19:33):

the FHIR specification never says that you must preserve precision. but your users will tell you that you must.

Grahame Grieve (Jul 12 2016 at 19:33):

note this comment:

Grahame Grieve (Jul 12 2016 at 19:34):

When using a JavaScript JSON.parse() implementation, note that JavaScript natively supports only one numeric datatype, which is a floating point number. This can cause loss of precision for FHIR numbers. In particular, trailing 0s after a decimal point will be lost e.g. 2.00 will be converted to 2. The FHIR decimal data type is defined such that precision, including trailing zeros, is preserved for presentation purposes, and this is widely regard as critical for correct presentation of clinical measurements. Implementations should consider using a custom parser and big number library (e.g. https://github.com/jtobey/javascript-bignum ) to meet these requirements.