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Measuring and Assessing Severity of Involvement for Children with SSD

Measuring and Assessing Severity of Involvement for Children with SSD. Peter Flipsen Jr., PhD, S-LP(C), CCC-SLP Professor of Speech-Language Pathology Idaho State University flippete@isu.edu (208) 373-1727. Outline. 1. What is severity? What factors affect severity?

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Measuring and Assessing Severity of Involvement for Children with SSD

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  1. Measuring and Assessing Severity of Involvement for Children with SSD Peter Flipsen Jr., PhD, S-LP(C), CCC-SLP Professor of Speech-Language Pathology Idaho State University flippete@isu.edu (208) 373-1727

  2. Outline • 1. What is severity? • What factors affect severity? • Defining severity categories? • Age differences? • 2. Assessing Severity

  3. Severity of Involvement • How Bad is the Problem? • Is it mild? • Is it moderate? • Is it severe? • Depends somewhat on the disorder (we will focus on children with SSD).

  4. Why is severity important? • Sometimes it isn’t. It may be enough to simply say there is a disorder. • But … • 1. It may affect access to service. • Some payers will limit what they will pay for depending on severity.

  5. Why is severity important? • 2. It may affect caseload management. • Clinicians may group clients by severity. • OR • We may see severe clients more often than mild ones.

  6. Why is severity important? • 3. It may influence our treatment choices. • For example: • conventional minimal pair therapy MAY be better for milder cases • cycles or multiple oppositions approaches MAY be better for more severe cases.

  7. What factors might affect severity? • How do we decide on severity? • In general we might consider: • 1. Specific skills the speaker may be lacking (disability). • Generally the easiest for us to measure.

  8. What factors might affect severity? • 2. Effect of skill reduction on the speaker’s daily functioning (handicap). • Difficult to measure. • Including a measure of “intelligibility” is probably as much as we normally do.

  9. Gold Standard? • Ideally we would have some ultimate standard or reference to compare against. • Might allow us to identify the relevant factors, but such a standard doesn’t exist. • The judgment of experienced clinicians is usually seen as the next best thing. • Dollaghan (2003) referred to such interim standards as a “tin standard”.

  10. What do experienced clinicians use? • Flipsen, Hammer, and Yost (2005) • Based on ratings from 6 very experienced clinicians (>10 years in the field) • Concluded that theyconsider: • Number of errors • Types of errors • Consistency of errors • Intelligibility • Accuracy at the sound and whole word level

  11. Defining Severity Categories • How many categories should we have? • Is mild, moderate, and severe enough? • Should we include profound? • Should we have intermediate categories? • No definitive answers. • May be defined for us by payers, administrators, or test developers. • May be left up to us to decide.

  12. Defining Severity Categories • How do we know what is mild vs. moderate vs. severe? • Where do we draw the line between the categories?

  13. Defining Severity Categories • Some norm-referenced speech sound tests offer severity categories with defined boundaries: • HodsonAssessment of Phonological Patterns-3 • Major DeviationsCategory • 1-50 Mild • 51-100 Moderate • 101-150 Severe • > 150 Profound

  14. Defining Severity Categories • Problems with boundaries set by test developers: • 1. They are usually arbitrary. • 2. Not clear how they would relate to boundaries used by a different test developer. • Hard to compare for transfer cases where clinicians use different tests.

  15. Age Considerations • Age is an important issue. • Clearly if a 7 year old and a 3 year old show similar speech performance, the older child will be of a greater concern. • Norm-referenced tests give us standard scores that account for age • BUT norm-referenced tests rely solely on number of errors and don’t consider other relevant factors. • They also rely solely on singe word productions which don’t always represent typical performance.

  16. Measuring Severity • Still lots of unanswered questions. • So what do we do? • Currently we don’t have any ideal measures available. • But we do have options.

  17. 1. Perceptual Rating Scales • Common practice. • Make a judgment based on listening and observing the child and assign them to a category. • A common 5 point scale might include: Normal, Mild, Moderate, Severe, Profound. • May include anywhere from 3-9 points. • Clinician uses whatever they feel is appropriate to make the judgment.

  18. Concerns with Rating Scales • 1. Different clinicians may consider different factors. • Ratings can vary considerably across clinicians. • E.g., Rafaat, Rvachew, and Russell (1995) had 15 clinicians (5+ years of experience) rate 45 children on a 5 point scale. • Only 61% exact agreement. • Even very experienced clinicians don’t agree very well. • Flipsen et al. (2005) found an intra-class correlation of 0.60 for the 6 clinicians on 17 samples.

  19. Concerns with Rating Scales • 2. Lack of reference standards. • Even if clinicians all considered the same factors, where do we draw the line between categories? • Different clinicians may draw the lines at different places. • Probably not the best approach.

  20. 2. PCC in conversation • One measure that has undergone some validation (and is often used in research) is Percentage Consonants Correct (PCC) from conversational speech samples. • Narrow phonetic transcription • Look at each attempt at a consonant and score as correct or incorrect. • Any change (including distortions) = error. • Calculate % correct over the entire sample.

  21. 2. PCC in conversation • Shriberg and Kwiatkowski (1982) had a large group (52) of clinicians rate severity on conversational speech samples. • Found that ratings matched well onto the following categories: • PCC rangeRating • 85+ Mild • 60-85 Mild-moderate • 50-65 Moderate-severe • <50 Severe

  22. Concerns with PCC • Doesn’t account for age. • Only looks at consonants. • Doesn’t consider other potentially important factors. • Based on conversational speech which is time consuming to evoke and transcribe.

  23. PCC and Age • More recently Austin and Shriberg (1997) published some reference data (not really norms) for PCC from conversational speech samples. • Provides means and standard deviations for males and females at different ages. • Allows for calculation of z-scores (# of standard deviations from the mean).

  24. 3. PCC in Imitated Sentences • To accommodate concerns with transcribing conversational speech, Johnson, Weston, and Bain (2004) developed a sentence imitation task. • Can score as child imitates each sentence (cross out any phonemes in error). • Simple calculation.

  25. 3. PCC in Imitated Sentences • Johnson et al showed that PCC in conversation was not significantly different from PCC on this task. • Useful alternative? • No age reference data available however.

  26. 4. Alternative Severity Measures • Several other measures might be used. For example: • Overall intelligibility (% words understood in conversation). • Shriberg et al (1997) proposed several variations on PCC • E.g., PVC, PPC, PCC-R • Ingram and Ingram (2001) proposed several measures that consider the whole word: • Phonological Mean Length of Utterance • Proportion of Whole Word Proximity • Proportion of Whole Word Variability

  27. 4. Alternative Severity Measures • Flipsen et al. (2005) compared many of these alternative measures to PCC. • Looked at how they correlated with ratings from very experienced clinicians. • Several were just as good but none of the alternatives appeared to be any better than PCC. • That included intelligibility. • Most involved more complicated calculations.

  28. Conclusions • Severity estimates are often very necessary. • To date we still don’t fully understand the best way to estimate severity. • We have several options available. • Perceptual rating scales should probably be avoided. • To date few of the available measures have been validated. • None so far seems any better than the oldest, objective measure – PCC.

  29. References • Austin, D., & Shriberg, L. D. (1997). Lifespan reference data for ten measures of articulation competence using the speech disorders classification system (SDCS) (Tech. Rep. No. 3). Phonology Project, WaismanCenter, University of Wisconsin‑Madison. • Dollaghan, C. A. (2003). One thing or another? Witches, POEMS, and childhood apraxia of speech. In Shriberg, L. D., & Campbell, T. F. (Eds.) Proceedings of the 2002 Childhood Apraxia of Speech Research Symposium (pp. 231-237). Carlsbad, CA: The Hendrix Foundation. • Flipsen, P., Jr., Hammer, J. B., & Yost, K. M. (2005).  Measuring severity of involvement in speech delay: Segmental and whole-word measures.  American Journal of Speech-Language Pathology, 14(4), 298-312. • Ingram, D., & Ingram, K. D. (2001). A whole-word approach to phonological analysis and intervention. Language, Speech and Hearing Services in Schools, 32, 271-283. • Johnson, C. A.,Weston, A. D., & Bain, B. A. (2004). An objective and time-efficient method for determining severity of childhood speech delay. American Journal of Speech-Language Pathology, 13, 55-65. • Rafaat, S. K., Rvachew, S., & Russell, R. S. C. (1995). Reliability of clinician judgments of severity of phonological impairment. American Journal of Speech-Language Pathology, 4(3), 39-46. • Shriberg, L. D., Austin, D., Lewis, B. A., McSweeny, J. L., & Wilson, D. L. (1997). The percentage of consonants correct (PCC) metric: extensions and reliability data. Journal of Speech, Language, and Hearing Research, 40, 708-722. • Shriberg, L. D., & Kwiatkowski, J. (1982). Phonological disorders III: A procedure for assessing severity of involvement. Journal of Speech and Hearing Disorders, 47, 256-270.

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