Measuring and assessing severity of involvement for children with ssd
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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 [email protected] (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

[email protected]

(208) 373-1727


Outline
Outline with SSD

  • 1. What is severity?

    • What factors affect severity?

    • Defining severity categories?

    • Age differences?

  • 2. Assessing Severity


Severity of involvement
Severity of Involvement with SSD

  • 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? with SSD

  • 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? with SSD

  • 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? with SSD

  • 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? with SSD

  • 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? with SSD

  • 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? with SSD

  • 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? with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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 with SSD

  • 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.


Conclusions
Conclusions with SSD

  • 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.


References
References with SSD

  • 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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