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Negation Detection in Swedish Clinical Text
Maria Skeppstedt
PhD Student atStockholm University
Department of Computer and Systems Sciences
Maria Skeppstedt, Louhi'10
Why do you need negation detection in clinical text?
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.
Maria Skeppstedt, Louhi'10
A first step towards Swedish negation detection
Maria Skeppstedt, Louhi'10
NegEx
By Wendy W Chapman, Will Bridewell, Paul Hanbury, Gregory F. Cooper, and Bruce G. Buchanan
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
…
Maria Skeppstedt, Louhi'10
Translation of negation triggers
• no ->ingen
• not -> inte
• no signs of -> inga tecken
• …
• not only -> inte bara
• …
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
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 codesFor example: “migraine, not specified” -> “migraine”
Maria Skeppstedt, Louhi'10
Classification of test data
1. 430 sentences
2. Affirmed, negated and ambiguous
Maria Skeppstedt, Louhi'10
Results, group 1, sentences with trigger phrases
Maria Skeppstedt, Louhi'10
Results, group 2, sentences without trigger phrases
Maria Skeppstedt, Louhi'10
Triggers for correctly identified negations
Maria Skeppstedt, Louhi'10
Precision for different triggers
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)
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)
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.
