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Negation Detection in Swedish Clinical Text Maria Skeppstedt PhD Student at Stockholm University Department of Computer and Systems Sciences.

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Presentation on theme: "Negation Detection in Swedish Clinical Text Maria Skeppstedt PhD Student at Stockholm University Department of Computer and Systems Sciences."— Presentation transcript:

1 Negation Detection in Swedish Clinical Text Maria Skeppstedt PhD Student at Stockholm University Department of Computer and Systems Sciences

2 Maria Skeppstedt, Louhi'10 Why do you need negation detection in clinical text?

3 Maria Skeppstedt, Louhi'10 Record X Since the patient has no headache, the patient does probably not have disease A. Record Y The patient has a headache.

4 Maria Skeppstedt, Louhi'10 A first step towards Swedish negation detection

5 Maria Skeppstedt, Louhi'10 NegEx By Wendy W Chapman, Will Bridewell, Paul Hanbury, Gregory F. Cooper, and Bruce G. Buchanan

6 Basic idea of NegEx Maria Skeppstedt, Louhi'10 Since the patient has no headache, … (headache) The patient has not only a headache, but also … (headache) Pre-Triggers no not no signs of … Post-Triggers unlikely … Pseudo negation not only …

7 Maria Skeppstedt, Louhi'10 Translation of negation triggers no ->ingen not -> inte no signs of -> inga tecken … not only -> inte bara …

8 Maria Skeppstedt, Louhi'10 Grammatical differences, Swedish and English, examples 1.Gender and number concord: ”no’’ -> ”inga” (plural), ”ingen” (common gender) and ”inget” (neuter gender) “no significant” -> ”inga signifikanta” (plural), “ingen signifkant” (common gender) and “inget signifikant” (neuter gender) 2.”denies/is denying” -> no grammatical equivalent in Swedish

9 Maria Skeppstedt, Louhi'10 Construction of test data 1.Diseases and symptoms from the describing text of the ICD-10 codes 2.Automatic pre-processing of ICD-10 codes For example: “migraine, not specified” -> “migraine”

10 Maria Skeppstedt, Louhi'10 Classification of test data sentences 2.Affirmed, negated and ambiguous

11 Maria Skeppstedt, Louhi'10 Results, group 1, sentences with trigger phrases

12 Maria Skeppstedt, Louhi'10 Results, group 2, sentences without trigger phrases

13 Maria Skeppstedt, Louhi'10 Triggers for correctly identified negations

14 Maria Skeppstedt, Louhi'10 Precision for different triggers

15 Maria Skeppstedt, Louhi'10 Examples of errors, that account for some of the difference 1.”inga egentliga märkbara symptom …” (no real noticeable symptoms …) 2.”Hon har inte huvudvärk, utan tandvärk ” (She has not headache, but toothache) 3. ”icke allergisk astma” (non-allergic asthma)

16 Maria Skeppstedt, Louhi'10 Examples of other errors 1.”Patienten har inte huvudvärk, men bröstsmär- tor.” (The patient has no headache, but chest pain) 2. ”Om inte huvudvärken har vikit...” (If not the headache has disappeared) 3.”Cirka hälften av alla med sjukdom A har inte symptom B” (About half of those with disease A, have no symptoms of B)

17 Maria Skeppstedt, Louhi'10 The next step 1.A list of conjunctions that limit the scope of the trigger. 2.Elaborate with adding or removing trigger phrases from the list. 3.Evaluation on a larger test set. 4.Detect the meaning of “utan” (but/without) in the context, and which cases that the trigger “not” negates.

18 Thank you! Questions? Maria Skeppstedt


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