why do i get different results ?

Why do I get different results ?

Terry Ann Jankowski, MLS, AHIPHead, User ExperienceHealth Sciences Library

University of Washington

Short Answer• Different databases• Term selection

Different Databases• Coverage– Years covered– Journals & publication types– Update schedule

• Structure– Default fields– Default operations

CoverageNLM PubMed/Medline• 1946 –• Daily (Tues – Sun)

Ovid Medline• Depends • Depends

What happens when you type

frozen shoulder

NLM• “All fields”• Automatic term mapping to

MeSH• Automatic explosion of

MeSH terms• Words “anded”

Ovid• “mp” – default fields• No term mapping• No explosion • Words searched as a phrase

What happens when you type

frozen shoulder*

NLM• “All fields”• No term mapping to MeSH• No explosion of MeSH

terms• Words searched as phrase

Ovid• “mp” – default fields• No term mapping• No explosion of MeSH• Words searched as phrase

What happens when you type

“frozen shoulder”

NLM• Phrase index searched• No explosion of MeSH

terms• Words searched as phrase

(may or may not be “anded”)

Ovid• “mp” – default fields• No term mapping• No explosion of MeSH• Words searched as phrase

You can control results by• Getting to know your database• Using qualifiers• Term selection

What terms to use?Natural language• Quick & dirty searching• New words, brand names,

phrases• Concepts not indexed

Controlled Vocabulary• More comprehensive?• Concepts not words• Pre-coordination

Indexing PrinciplesEntire articleAvg 10 – 15/20Major vs minorUse most specific term or closest match – Rule of 3Drugs – generic (USAN)Techniques, methods & geography – minor onlyNeoplasms - site & histological typeSpecialty terms

Indexing Rules of Thumb• Pre-coordinated• Heading/sub heading combination(s)• 2 or more unrelated terms

Warning• Inconsistency in indexing

Question

• What is the effect of estrogen and progesterone on the brain, particularly in regards to epilepsy?

Natural Language Strategy

Brain AND (estrogen OR progesterone) AND (epilepsy OR seizures)

Controlled Vocabulary Search(brain/de OR brain/ci) AND (estrogens OR progesterone) AND (epilepsy/ci OR epilepsy/ci)

CompareBrain-derived neurotrophic factor-estrogen interactions in the hippocampal mossy fiber pathway: Implications for normal brain function and disease. PMID: 23276673 [PubMed - in process] Finasteride inhibits the disease-modifying activity of progesterone in the hippocampus kindling model of epileptogenesis. PMID: 22835430 [PubMed - indexed for MEDLINE]

Which will you use?

Final Thoughts• Experiment to find the best search• Use the database structure and features to

your advantage• KNOW YOUR DATABASE