The value of a simple quantitative test method
A recent warning from the Institute for Safe Medication Practices Canada (ISMPC) (https://www.ismp-canada.org/download/safetyBulletins/2019/ISMPCSB2019-i7-PEG-Thickener.pdf) illustrates the value of the simple flow test developed by the International Dysphagia Diet Standardisation Initiative (IDDSI) and proper training.
In this case, a patient was served a juice that became unthickened due to an interaction between a laxative and the thickener used with the juice. The report states “The healthcare provider preparing and administering the mixture was unfamiliar with the appearance of different types of thickened liquids. In particular, the change in consistency after the PEG laxative was added, from thickened to thin and watery, went unnoticed.”
Among the many recommendations of the ISMPC, is this one (my emphasis added):
Educate front-line staff and patients/families about the potential for harm if a patient with dysphagia receives PEG laxative dissolved in a liquid thickened with a starch-based thickener. Highlight the importance of conducting a visual check of the thickened product’s texture before administering it to a patient with dysphagia.
It is well understood today that visual appearances are not an acceptable test for proper thickness. It might be ok for the simple binary choice of “is it thick? or is it not thick?”, but it is not a great way to ensure proper thickness. But the ISMPC has missed the mark with this recommendation.
The IDDSI flow test is a fast simple, inexpensive and quite good test to ensure the proper consistency of liquids. The IDDSI flow test uses a particular 10 mL syringe and is able to properly differentiate liquid consistencies with this 10 second test. The test is conducted by filling the syringe with 10 mL of the test beverage and checking how much is left after 10 seconds. One recent study (https://doi.org/10.1111/jtxs.12360) found a 90% correlation between the flow test and a “sophisticated computer-controlled rheometer” (r2=0.897).
The ISMPC would have moved patient safety forward even more with a simple recommendation like:
Educate front-line staff and patients/families about the potential for harm if a patient with dysphagia receives PEG laxative dissolved in a liquid thickened with a starch-based thickener. Highlight the importance of conducting a consistency check with a quantitative test method (like the IDDSI Flow Test) of the thickened product’s texture before administering it to a patient with dysphagia.
FULL REFERENCE: Kim Y-H, Jeong GY, Yoo B. Comparative study of IDDSI test and line-spread test of thickened water prepared with different dysphagia thickeners. J Texture Stud. 2018;49:653-658.