Evidence map›Paper›PMID 25551437›Full record

ReviewSystematic reviews2014

Recovering the raw data behind a non-parametric survival curve.

Zhihui Liu, Benjamin Rich, James A Hanley

Abstract readReview
PubMed Full text at PMC Publisher
In one paragraph

Review in Systematic reviews, 2014. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 24 papers, 13 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
24citing papers in PubMed, 13 pooled it
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

24 citing papers in PubMed, 13 syntheses or guidelines pooled it.

  1. Effect of Excessive Daytime Sleepiness and Long Sleep Duration on All Cause Dementia: A Systematic Review and Meta-analysis.The journals of gerontology. Series A, Biological sciences and medical sciences · 2025
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  16. Calculating the Expected Net Benefit of Sampling for Survival Data: A Tutorial and Case Study.Medical decision making : an international journal of the Society for Medical Decision Making · 2024
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4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

3 authors.

Zhihui Liu
Benjamin Rich
James A HanleyDepartment of Epidemiology, Biostatistics and Occupational Health, McGill University, 1020 Pine Avenue West, H3A 1A2, Montreal, Canada. james.hanley@mcgill.ca.

Funding

Canadian Institutes of Health Research
6 · The paper itself

Abstract

backgroundResearchers often wish to carry out additional calculations or analyses using the survival data from one or more studies of other authors. When it is not possible to obtain the raw data directly, reconstruction techniques provide a valuable alternative. Several authors have proposed methods/tools for extracting data from such curves using a digitizing software. Instead of using a digitizer to read in the coordinates from a raster image, we propose directly reading in the lines of the PostScript file of a vector image.

methodsUsing examples, and a formal error analysis, we illustrate the extent to which, with what accuracy and precision, and in what circumstances, this information can be recovered from the various electronic formats in which such curves are published. We focus on the additional precision, and elimination of observer variation, achieved by using vector-based formats rendered by PostScript, rather than the lower resolution image-based formats that have been analyzed up to now. We provide some R code to process these.

resultsIf the raster-based images are available, one can reliably recover much of the original information that seems to be 'hidden' beneath published survival curves. If the original images can be obtained as a PostScript file, the data recovered from it can then be either input into these tools or processed directly. We found that the PostScript used by Stata discloses considerably more of the data hidden behind survival curves than that generated by other statistical packages.

conclusionsWhen it is not possible to obtain the raw data from the authors, reconstruction techniques are a valuable alternative. Compared with previous approaches, one advantage of ours is that there is no observer variation: there is no need to repeat the digitization process, since the extraction is completely replicable.

Indexed as

Survival AnalysisKaplan-Meier EstimateStatistics, Nonparametric

Identifiers

PMID25551437
PMCPMC4293001

What OpenQuestion holds

Textmetadata
LicenceCC BY
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.