IDDSI Framework Testing Methods
INTRODUCTION
The International Dysphagia Diet Standardisation Initiative (IDDSI) was founded in 2013 with the goal of developing new global standardised terminology and definitions to describe texture modified foods and thickened liquids used for individuals with dysphagia of all ages, in all care settings, and all cultures.
Three years of ongoing work by the International Dysphagia Diet Standardisation Committee has culminated in a final dysphagia diet framework consisting of a continuum of 8 levels (0-‐7). Levels are identified by numbers, text labels and colour codes.
This document provides details regarding Testing Methods for use with the IDDSI Framework.
This document is to be read in conjunction with the Complete IDDSI Framework, IDDSI Evidence and
IDDSI Frequently Asked Questions (FAQs) documents (http://iddsi.org/resources/framework/).
The IDDSI Committee would like to acknowledge the interest and participation of the global community including patients, caregivers, health professionals, industry, professional associations and researchers. We would also like to thank our sponsors for their generous support.
Please visit the www.iddsi.org for further information
The IDDSI Committee:
Co-‐Chairs: Peter Lam (CAN) & Julie Cichero (AUS);
Committee Members: Jianshe Chen (CHN), Roberto Dantas (BRA), Janice Duivestein (CAN), Ben Hanson (UK), Jun Kayashita (JPN), Caroline Lecko (UK), Mershen Pillay (ZAF), Luis Riquelme (USA), Soenke Stanschus (GER), Catriona Steele (CAN).
Past Committee Members: Joe Murray (USA)
The International Dysphagia Diet Standardisation Initiative Inc. (IDDSI) is an independent, not-‐for-‐profit entity. IDDSI is grateful to a large number of agencies, organizations and industry partners for financial and other support. Sponsors have not been involved with the design or development of the IDDSI framework.
Development of the IDDSI framework (2012-‐2015)
IDDSI would like to thank and acknowledge the following sponsors for their generous support in the development of the IDDSI framework:
· Nestlé Nutrition Institute (2012-‐2015)
· Nutricia Advanced Medical Nutrition (2013-‐2014)
· Hormel Thick & Easy (2014-‐2015)
· Campbell’s Food Service (2013-‐2015)
· apetito (2013-‐2015)
· Trisco (2013-‐2015)
· Food Care Co. Ltd. Japan (2015)
· Flavour Creations (2013-‐2015)
· Simply Thick (2015)
· Lyons (2015)
Implementation of the IDDSI framework is in progress. IDDSI is extremely grateful to all sponsors supporting implementation http://iddsi.org/about-‐us/sponsors/
Testing Methods for use with the IDDSI Framework
The IDDSI systematic review suggested that liquids and food should be classified in the context of the physiological processes involved in oral processing, oral transport and flow initiation. To this end, different devices are needed to best describe the behaviour of the bolus (Steele et al., 2015).
Drinks and other liquids
Accurate measurement of fluid flow properties is a complex task. To date, both research and existing national terminologies, have studied or recommended the classification of drinks based on viscosity. However, viscosity measurement is not accessible to most clinicians or caregivers.
Furthermore, viscosity is not the only relevant parameter: the flow of a drink as it is consumed is influenced by many other variables including density, yield stress, temperature, propulsion pressure and fat content (O`Leary et al., 2010; Sopade et al., 2007, Sopade et al., 2008a,b; Hadde et al.2015a,b). The systematic review demonstrated wide variability in testing techniques used and found that other key parameters such as shear rates, sample temperature, density and yield stress were rarely reported (Steele et al., 2015; Cichero et al., 2013). Drinks thickened with different thickening agents may have the same measurement of apparent viscosity at one particular shear rate, and yet have very different flow characteristics in practice (Steele et al. 2015; O`Leary et al.,2010; Funami et al., 2012; Ashida et al., 2007; Garcia et al., 2005). In addition to variations in flow associated with drink characteristics, flow rates during swallowing are expected to differ depending on a person`s age and level of impairment of swallowing function (O`Leary et al., 2010).
For these reasons, a measurement of viscosity has not been included in the IDDSI descriptors. Instead, a gravity flow test using a 10 mL slip tip syringe is recommended to quantify the liquid`s flow category (sample remaining from 10 mL after 10 sec of flow). The controlled conditions are broadly representative of drinking through a straw or beaker.
The IDDSI Flow test is also similar in design and measurement principles to the Posthumus Funnel that is used in the dairy industry to measure liquid thickness (van Vliet, 2002; Kutter et al., 2011). In fact the Posthumus funnel looks like a large syringe (van Vliet, 2002; Kutter et al., 2011). Measures taken using the Posthumus funnel include the time for a specified amount of sample to flow, and mass left after a defined period of flow. Van Vliet (2002) notes that the geometry of the Posthumus funnel contains a shear and elongation component that more closely matches flow conditions within the oral cavity.
Although the syringe chosen for use with the IDDSI Flow test is simple, the test has been found to categorise a wide range of liquids reliably, and in agreement with currently existing laboratory tests and expert judgement. It has also been found to be sensitive enough to demonstrate small changes in thickness associated with change in serving temperature.
IDDSI Flow Test
The IDDSI Flow test uses a 10 mL slip tip hypodermic syringe, as shown in the image below.
Although 10 mL syringes were initially thought to be identical throughout the world based on reference to an ISO standard (ISO 7886-‐1), it has subsequently been determined that the ISO document refers only to the nozzle of the syringe and that variability in barrel length and dimensions may exist between brands. Specifically the IDDSI Flow test uses a reference syringe with a measured length of 61.5 mm from the zero line to the 10 mL line (BDTM syringes were used for the development of the tests – manufacturer code 301604). IDDSI is aware that there are some syringes that are labeled as 10 mL, but in fact have a 12 mL capacity. Results using a 12 mL syringe will be different to those from a true 10 mL syringe. As a result it is important to check the barrel length as shown on the diagram below. Details for conducting the test are shown below.
Videos showing the IDDSI Flow Test can also be viewed at: http://iddsi.org/framework/drink-‐testing-‐ methods/
Drinks and liquids such as gravy, sauces and nutritional supplements are best assessed using the IDDSI Flow Test (Levels 0-‐3). For extremely thick drinks (Level 4), that do not flow through a 10 mL syringe in 10 seconds and are best consumed with a spoon, the IDDSI Fork Test and/or Spoon Tilt Test are recommended as methods for determining consistency.
Foods
Research to date in the area of food texture measurement requires complex and expensive machinery such as Food Texture Analysers. Given the difficulty with access to such equipment and the expertise required for testing and interpretation, many existing national terminologies have used detailed descriptors to describe food texture instead.
The systematic review demonstrated that the properties of hardness, cohesiveness and slipperiness were important factors for consideration (Steele et al., 2015). In addition, size and shape of food samples have been identified as relevant factors for choking risk (Kennedy et al., 2014; Chapin et al., 2013; Japanese Food Safety Commission, 2010; Morley et al., 2004; Mu et al., 1991; Berzlanovich et al. 1999; Wolach et al., 1994; Centre for Disease Control and Prevention, 2002, Rimmell et al., 1995; Seidel et al., 2002).
In view of this information, measurement of foods needs to capture both the mechanical properties (e.g. hardness, cohesiveness, adhesiveness etc.) and the geometrical or shape attributes of the food. The IDDSI descriptions of food texture and characteristics, food texture requirements and restrictions have been generated from existing national terminologies and the literature describing properties that increase risk for choking.
A combination of tests may be required to determine which category a food fits into. Testing methods for purees, soft, firm and solid foods include: The Fork Drip test, Spoon Tilt test, Fork or Spoon Pressure Test, Chopstick Test and Finger test. Videos showing examples of these testing methods can be found at: http://iddsi.org/framework/food−testing−methods/
Fork Drip Test
Thick drinks and fluid foods (Levels 3 and 4) can be tested by assessing whether they flow through the slots/prongs of a fork and comparing against the detailed descriptions of each level. Fork drip tests are described in existing National terminologies in Australia, Ireland, New Zealand and the United Kingdom (Atherton et al., 2007; IASLT and Irish Nutrition & Dietetic Institute 2009; National Patient Safety Agency, Royal College Speech & Language Therapists, British Dietetic Association, National Nurses Nutrition Group, Hospital Caterers Association 2011).
Images for Level 3 − Liquidised/Moderately Thick are shown below.
Images for Level 4 − Pureed/Extremely Thick are shown below.
Spoon Tilt Test
The spoon tilt test is used to determine the stickiness of the sample (adhesiveness) and the ability of the sample to hold together (cohesiveness). The Spoon Tilt Test is described in existing National terminologies in Australia, Ireland, New Zealand and the United Kingdom (Atherton et al., 2007; IASLT and Irish Nutrition & Dietetic Institute 2009; National Patient Safety Agency, Royal College Speech & Language Therapists, British Dietetic Association, National Nurses Nutrition Group, Hospital Caterers Association 2011).
The Spoon Tilt Test is used predominantly for measures of samples in levels 4 and 5. The sample should:
• Be cohesive enough to hold its shape on the spoon
• A full spoonful must slide/pour off the spoon if the spoon is tilted or turned sideways or shaken lightly; the sample should slide off easily with very little food left on the spoon; i.e. the sample should not be sticky
• A scooped mound may spread or slump very slightly on a plate
Soft, firm and hard food texture assessment
For soft, hard or firm food, the fork has been chosen to assess food texture as it can uniquely be used for assessment of mechanical properties associated with hardness, in addition to assessment of shape attributes such as particle size.
Assessing for 4mm particle size compliance
For adults, the average particle size of chewed solids foods before swallowing measures 2−4 mm (Peyron et al., 2004; Woda et al., 2010). The slots/gaps between the tines/prongs of a standard metal fork typically measure 4 mm, which provides a useful compliance measure for particle size of foods at Level 5 Minced & Moist. For determining particle size safety for infants, samples that are smaller than the maximum width of the child`s fifth fingernail (littlest finger) should not cause a choking risk as this measurement is used to predict the internal diameter of an endotracheal tube in the paediatric population (Turkistani et al., 2009).
Compliance with 4mm particle size can be demonstrated with a fork as shown in the images opposite.
Assessing for 15mm (1.5cm) particle size compliance
For hard and soft solid foods, a maximum food sample size of 1.5 x 1.5 cm is recommended, which is the approximate size of the adult human thumb nail (Murdan, 2011). The entire width of a standard fork also measures approximately 1.5cm as shown in the images below. 1.5 x 1.5 cm particle size is recommended for Level 6 − Soft & Bite−sized to reduce risk associated with asphyxiation from choking on food (Berzlanovich et al., 2005; Bordsky et al., 1996; Litman et al., 2003).
Fork Pressure Test and Spoon Pressure Test
A fork can be applied to the food sample to observe its behaviour when pressure is applied. Pressure applied to the food sample has been quantified by assessment of the pressure needed to make the thumb nail blanch noticeably to white, as demonstrated by the arrows in the image at left.
The pressure applied to make the thumb nail blanch has been measured at ~ 17 kPa. This pressure is consistent with tongue force used during swallowing (Steele et al., 2014). In the image at right, pressure is being demonstrated in kilopascals using an Iowa Oral Performance Instrument. This is one device that can be used to measure tongue pressure.
For assessment using the Fork Pressure Test, it is recommended that the fork be pressed onto the food sample by placing the thumb onto the bowl of the fork (just below the prongs) until blanching is observed, as shown in the image at left. It is appreciated that forks are not readily available in some parts of the world. Pressure applied using the base of a teaspoon may provide a useful alternative.
Chopstick Test and Finger test
Assessment with chopsticks has been included in the IDDSI. Finger tests have been incorporated in recognition that this may be the most accessible method in some countries.
Transitional food texture assessment
Transitional food textures are those that start as one texture (e.g. firm solid) and change into another texture specifically when moisture (e.g. water or saliva) is applied, or when a change in temperature occurs (e.g. heating). This food texture is used in developmental teaching or rehabilitation of chewing skills. For example it has been used in the development of chewing in the paediatric population and developmental disability population (Gisel 1991; Dovey et al., 2013).
To assess whether a sample fits the definition of a transitional food, the following method is applied:
Use a sample the size of the thumb nail (1.5 cm x 1.5 cm), place 1 ml of water on the sample and wait one minute. Apply fork pressure using the base of the fork until the thumbnail blanches to white. The sample is a transitional food texture if after removing the fork pressure:
· The sample has been squashed and disintegrated and no longer looks like its original state when the fork is lifted
· The sample can be easily broken apart using chopsticks with minimal pressure.
· The sample breaks apart completely by rubbing the sample between the thumb and index finger and does not return to its initial shape.
· Or it has melted significantly and no longer looks like its original state (e.g. ice chips).
Future studies
Further work is required to develop an inexpensive but accurate tool to assist with food texture analysis
*Accompanying documents (http://iddsi.org/framework/):
Ø IDDSI Testing Methods
Ø IDDSI Evidence
Ø IDDSI Frequently Asked Questions (FAQs