Analysis of prognosis filter performance
This protocol is extracted from research article:
Search methods for prognostic factor systematic reviews: a methodologic investigation
J Med Libr Assoc, Jan 1, 2021; DOI: 10.5195/jmla.2021.939

We conducted a performance analysis of the prognosis filter used in Hayden et al.'s review (Irvin filter) [29] compared with three other known filters: the optimized version of a filter developed by the Hedges Team at McMaster University (“Hedges Optimized” filter) [9]; an inclusive, general filter developed by Parker et al. (“Inclusive General” filter) [30]; and another filter developed by Parker et al. combining all of the Hedges Team's filters [9] plus the keywords “natural history” (“Combined Hedges + Natural History” filter) [30]. Table 1 shows the details of all filters we analyzed in Ovid MEDLINE format. Although the four filters contain similar terms, they demonstrate the slight variance in language that is often used when searching for prognosis studies. Through our analysis, we explored whether these minute differences affected recall.

Details of prognosis filters analyzed, Ovid MEDLINE format

Cohort Studies/


Follow-Up Studies/



Survival Analysis/


exp models, statistical/





follow-up study.ti,ab.

follow-up studies.ti,ab.




natural history.ti,ab.



exp Mortality/

Follow-Up Studies/




(first and episode).ti,ab.




The performance analysis measured operating characteristics for each filter against a reference standard of records in Ovid MEDLINE using formulae outlined by Kok et al. [31] and Gehanno et al. [32]. To provide richer ground for analysis, we wanted to expand our reference standard beyond the sixty studies included in the final stage of Hayden et al.'s review. As detailed in the original Hayden et al. review, to mitigate the risk of introducing bias by including prognostic factor terms in the electronic search, the team advanced all citations—retrieved by any of the search methods detailed thus far—of low back pain prognostic factor studies, regardless of the presence or absence of the specific prognostic factor of interest. We, therefore, drew the reference standard from prognosis studies that were included at the first stage of screening in the review. We used the reference standard to calculate each filter's sensitivity, precision, number needed to read (NNR), specificity, and accuracy.

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