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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 (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

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

(208) 373-1727

  • 1. What is severity?
    • What factors affect severity?
    • Defining severity categories?
    • Age differences?
  • 2. Assessing Severity
severity of involvement
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).
why is severity important
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.
why is severity important1
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.
why is severity important2
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.
what factors might affect severity
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.
what factors might affect severity1
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.
gold standard
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”.
what do experienced clinicians use
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
defining severity categories
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.
defining severity categories1
Defining Severity Categories
  • How do we know what is mild vs. moderate vs. severe?
    • Where do we draw the line between the categories?
defining severity categories2
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
defining severity categories3
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.
age considerations
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.
measuring severity
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.
1 perceptual rating scales
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.
concerns with rating scales
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.
concerns with rating scales1
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.
2 pcc in conversation
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.
2 pcc in conversation1
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
concerns with pcc
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.
pcc and age
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).
3 pcc in imitated sentences
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.
3 pcc in imitated sentences1
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.
4 alternative severity measures
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
4 alternative severity measures1
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.
  • 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.
  • 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.