H-index pathology: implications for medical researchers and practitioners

The use of the Hirsch index in benchmarking hepatic surgery research

BACKGROUND

The Hirsch index (h-index) is recognized as an effective way to summarize an individual's scientific research output. However, a benchmark for evaluating surgeon scientists in the field of hepatic surgery is still not available.

METHODS

A total of 3,251 authors who published between 1949 and 2011 were identified using the Scopus identification number. The h-index, the total number of cited document, the total number of citations, and the scientific age were calculated for each author using both Scopus and Google Scholar.

RESULTS

The median h-index was 6 and the median scientific age, assessed with Google Scholar, was 19 years. The numbers of cited documents, numbers of citations, and h-indexes obtained from Scopus and Google Scholar showed good correlation with one another; however, the results from the 2 databases were modified in different ways by scientific age. By plotting scientific age against h-index percentiles an h-index growth chart for both Scopus database and Google Scholar was provided.

CONCLUSIONS

This analysis provides a first benchmark to assess surgeon scientists' productivity in the field of liver surgery.

Ranking hepatologists: which Hirsch's h-index to prevent the "e-crise de foi-e"?

BACKGROUND

Hirsch's h-Index (h-I) quantifies and predicts an individual's scientific output. The h-I can be estimated from several sources, but no "gold-standard" approach has yet been established. The aim was to analyze the discordance rates in Hepatology between five h-I assessments from five databases: Scholar, Scopus, Web of Science (WoS), ScholarL restricted to "liver", and a specialty h-I HepaTop.

METHODS

The reference for the main endpoint was "h-I 50", the median of included authors. Applicability and accuracy were assessed among 158 authors identified in the top 100 of the most cited "clinical" Hepatologists by two independent sources. The accuracy assessment used the area under the receiver operating characteristics curves (AUROCs) standardized or not according to spectrum effect, and the Pearson (PCC), and intraclass (ICC) coefficients of correlation.

RESULTS

Performances varied significantly according to h-I (P<0.001). Applicability was 80% for h-HepaTop and 100% for other h-I. AUROCs ranged from 0.55 (h-Scholar) to 0.88 (h-HepaTop). The h-I were highly inter-correlated but without perfect concordance: ICCs ranged from 0.01 (h-WoS versus h-Scholar) to 0.53 (h-WoS versus h-Scopus; P<0.0001). There were no differences between the AUROCs for h-Scopus, h-WoS and h-HepaTop, with lower accuracy for h-Scholar. The h-WoS AUROC adjusted for risk factors, scientific age and homonymy, increased in combination with h-HepaTop from 0.83 to 0.94 P=0.005.

CONCLUSIONS

The h-I should be carefully checked before any hepatologist's evaluation. Three factors were associated with applicability and accuracy: the data source, the risk of homonyms, and scientific age. A unique "global" identification number is warranted.

Hirsch index and truth survival in clinical research

Background

Factors associated with the survival of truth of clinical conclusions in the medical literature are unknown. We hypothesized that publications with a first author having a higher Hirsch' index value (h-I), which quantifies and predicts an individual's scientific research output, should have a longer half-life.

Methods and Results

474 original articles concerning cirrhosis or hepatitis published from 1945 to 1999 were selected. The survivals of the main conclusions were updated in 2009. The truth survival was assessed by time-dependent methods (Kaplan Meier method and Cox). A conclusion was considered to be true, obsolete or false when three or more observers out of the six stated it to be so. 284 out of 474 conclusions (60%) were still considered true, 90 (19%) were considered obsolete and 100 (21%) false. The median of the h-I was = 24 (range 1–85). Authors with true conclusions had significantly higher h-I (median = 28) than those with obsolete (h-I = 19; P = 0.002) or false conclusions (h-I = 19; P = 0.01). The factors associated (P<0.0001) with h-I were: scientific life (h-I = 33 for>30 years vs. 16 for<30 years), -methodological quality score (h-I = 36 for high vs. 20 for low scores), and -positive predictive value combining power, ratio of true to not-true relationships and bias (h-I = 33 for high vs. 20 for low values). In multivariate analysis, the risk ratio of h-I was 1.003 (95%CI, 0.994–1.011), and was not significant (P = 0.56). In a subgroup restricted to 111 articles with a negative conclusion, we observed a significant independent prognostic value of h-I (risk ratio = 1.033; 95%CI, 1.008–1.059; P = 0.009). Using an extrapolation of h-I at the time of article publication there was a significant and independent prognostic value of baseline h-I (risk ratio = 0.027; P = 0.0001).

Conclusions

The present study failed to clearly demonstrate that the h-index of authors was a prognostic factor for truth survival. However the h-index was associated with true conclusions, methodological quality of trials and positive predictive values.