Worldwide Use of RUCAM for Causality Assessment in 81,856 Idiosyncratic DILI and 14,029 HILI Cases Published 1993–Mid 2020: A Comprehensive Analysis

Background: A large number of idiosyncratic drug induced liver injury (iDILI) and herb induced liver injury(HILI) cases of variable quality has been published but some are a matter of concern if the cases were not evaluated for causality using a robust causality assessment method (CAM) such as RUCAM (Roussel Uclaf Causality Assessment Method) as diagnostiinjuryc algorithm. The purpose of this analysis was to evaluate the worldwide use of RUCAM in iDILI and HILI cases. Methods: The PubMed database (1993–30 June 2020) was searched for articles by using the following key terms: Roussel Uclaf Causality Assessment Method; RUCAM; Idiosyncratic drug induced liver injury; iDILI; Herb induced liver injury; HILI. Results: Considering reports published worldwide since 1993, our analysis showed the use of RUCAM for causality assessment in 95,885 cases of liver injury including 81,856 cases of idiosyncratic DILI and 14,029 cases of HILI. Among the top countries providing RUCAM based DILI cases were, in decreasing order, China, the US, Germany, Korea, and Italy, with China, Korea, Germany, India, and the US as the top countries for HILI. Conclusions: Since 1993 RUCAM is certainly the most widely used method to assess causality in IDILI and HILI. This should encourage practitioner, experts, and regulatory agencies to use it in order to reinforce their diagnosis and to take sound decisions.


Worldwide Publications of DILI
The current scientometric report from China on knowledge mapping confirmed the high worldwide interest in DILI publications and identified a total of 1995 DILI studies published between 2010 and 2019, although information on the applied method of causality assessment was not provided and will need further clarification [1]. This Chinese analysis on the top 10 countries involved in DILI research listed the US, China, Japan, Germany, UK, Spain, France, the Netherlands, Sweden, and Canada. In addition, many interesting details on DILI were comprehensively discussed with focus on definition, incidence rate, clinical characteristics, etiology or pathogenesis such as the character of the innate immune system, the regulation of cell-death pathways, susceptible HLA (Human Leukocyte Antigen) identification, or criteria and methods of causality assessment, all topics were considered as the knowledge base for DILI research [1].

Worldwide Publications of RUCAM Based Idiosyncratic DILI
The worldwide impact of DILI can best be quantified by using liver injury cases assessed for causality with a robust method that allows for establishing causality gradings for each implicated drug and to exclude alternative causes unrelated to drug administration.

Countries and Regions
In the current analysis, authors from 31 countries worldwide reported on cases of idiosyncratic DILI caused by multiple drugs published from 1993 up to mid 2020 and applied in all cases RUCAM to assess causality (Table 1)  . Such a table with a comprehensive list of publications over a long period has never been reported before and will facilitate the search for RUCAM based DILI cases caused by individual drugs, considering that databases such as LiverTox may have problems providing real DILI cases [10,74].

Hospital and Other Sources
RUCAM based DILI cases were mostly published by authors from university hospitals and their affiliated teaching hospitals known for their high reputation (Table 1). Among these were a broad range of departments, which in most cases include departments of Hepatology and Gastroenterology, ensuring careful clinical evaluation of patients with suspected DILI and associated causality assessment for the offending drug(s). To a lesser degree, other departments were contributors, for instance, Pharmacology, or Pharmacy and Pharmaceutical sciences [170]. In addition to hospitals, other sources provided RUCAM based DILI cases (Table 1). Among these were National Institutes of Health from Japan [92] and the US [165], consortia from Spain [115,141], the adverse drug reactions advisory committee (ADRAC) from Sweden [126], regulatory pharmacovigilance and pharmacoepidemiology centers from France [58,59] and Italy [86], drug commission of medical association from Germany [64], committee for drug induced liver injury from China [42]; also, drug reaction reporting database from Spain [65], regulatory agency from Spain [114] health insurance from the US [157], and drug safety departments of drug companies from France [57], Sweden {148], and Switzerland [132]. Some of these played an eminent role in promoting the use of RUCAM in prospective studies, particularly those from Spain [115], Sweden [126], and the US with France and Sweden [148].

Top Ranking Countries
Among the top 10 countries were in decreasing order China, the US, Germany, Korea, Italy, Sweden, Spain, Japan, Argentina, and Thailand, whereby the top 5 countries provided most of the DILI cases (Table 2). Authors from these 5 countries contributed together 75,133 DILI cases out of a total 81,856 worldwide DILI cases, corresponding to 91.8%. On the lower part of the list ranked the 6 countries Israel, Malaysia, Mexico, Morocco, Saudi Arabia, and Turkey, authors from these low ranking countries provided each one single DILI case assessed for causality using RUCAM, corresponding to 6 cases altogether out of a total of 81,856 DILI cases. Authors from the remaining 20 countries with a ranking from 6 down to 25 contributed 6.723 DILI cases out of overall 81,856 cases corresponding to 8.2%. In essence, RUCAM based DILI cases were mostly published in English language journals, raising the question how DILI cases were assessed and published by the other countries in local journals in languages other than English. Currently, overall 81,856 cases of idiosyncratic DILI assessed for causality by RUCAM have been retrieved via PubMed, all published 1993-June 2020 (Table 1) .

Annual Growth Trends of RUCAM Based DILI Case Publications
Analyses of growth trends provided additional information after identification of a total 1995 DILI studies, published between 2010 and 2019 but not stratified for causality assessment using RUCAM [1]. In the frame of the present analysis, only publications of idiosyncratic DILI cases were included if they had been assessed for causality using RUCAM, providing a more homogenous series with established DILI diagnoses. Phase 1 started after the launch of RUCAM in 1993 [16,47] and the analysis of 94 DILI cases [47], the number of subsequent annual published DILI cases remained small until 2004, reaching 121 cases ( Figure 1). This was the period of initial testing the RUCAM algorithm under clinical field conditions with interesting early information provided by 3 reports [58,91,114]. The first report came from Spain, was published in 1996, analyzed a major study cohort of DILI due to amoxicillin and clavulanate, and described their typical clinical features, with Rodríguez as first author and Zimmerman as senior author [114] who actually was involved as an expert from the US in the international consensus meetings [14] but did not promote RUCAM in DILI evaluations in his own country. Of interest was also the retrospective design of this analysis, suggesting that this particular study approach is feasible [114] although a prospective approach is recommended [15]. The second report was from Japan with Japanese patients, published in 2003 by Masumoto et al. [91]. This study favored RUCAM over other CAMs, provided evidence that the performance of the lymphocyte transformation test was poor in line with previous reports, and the RUCAM criteria were viewed as useful for diagnosing DILI in Japanese patients. The third publication came from France, reported in 2004 on details of a patient with DILI by pioglitazone, and showed the feasibility of a good case report to be assessed by RUCAM, evaluated by Arotcarena et al. [58]. All three reports were hallmarks of the first phase of RUCAM based DILI case series devoted to clinical field evaluation that ended in 2004 ( Figure 1).  Figure 1) [115,126,147,148]. Among these were 461 cases provided by Andrade et al. from Spain retrieved from a prospective study involving various drugs [115], additional 784 cases from Sweden were published by Björnsson and Olsson retrieved from a prospective study of DILI by various drugs [126], whereas from the US 2 case reports of DILI by amoxicillin and clavulanate were presented by Fontana et al. [147] as well as a large cohort of DILI caused by ximelagatran occurred in clinical trials was published by Lee et al. [148]. These 4 studies promoted the usefulness of RUCAM evaluating DILI cases [115,126,147,148] by preferring a prospective study design [115,126], evaluating single DILI case reports [147], and correctly assessing suspected DILI cases in clinical trials [148]. Whereas RUCAM had already a firm place among DILI experts in Europe, it seems that experts in the US became more familiar with the use and practicability of RUCAM. Phase 3 is characterized by the worldwide use of RUCAM for DILI started in 2014 with 11,525 DILI cases (Figure 1), mostly attributed to one study with 11,109 DILI cases provided by Cheetham et al. [157].
Starting in 2015, there was a continuous rise of published RUCAM based DILI cases (Figure 1), likely driven also by the updated RUCAM available online 2015 and published in 2016 [15]. With 27,224 published DILI cases, the maximum level on an annual base was achieved in 2019 ( Figure 1). Until end of June 2020, additional 15,153 published DILI cases were counted but not included in Figure 1, corresponding already to more than half of the cases counted in 2019 and representing a good base for 2020 and further years.
DILI studies, published between 2010 and 2019 but not stratified for causality assessment using RUCAM [1]. In the frame of the present analysis, only publications of idiosyncratic DILI cases were included if they had been assessed for causality using RUCAM, providing a more homogenous series with established DILI diagnoses.

Annual RUCAM Based DILI Publications and Growth Trend
Over the years starting from 1993, when RUCAM was launched [14,57], and until 2019 an upward trend of annual RUCAM based DILI publications can be observed with some dips in between (Figure 2). In 2019, 26 publications were counted, and 15 publications from January 2020 until end of June 2020 that were not included in the listing (Figure 2). Overall 158 publications with RUCAM based DILI cases were counted from 1993 until mid 2020 (Table 1).

Specificities of DILI Case Evaluation
Large study cohorts of RUCAM based DILI cases accumulated many different drugs and provided as expected a global information of the DILI cases due to various drugs without a detailed description of clinical features drug by drug (Table 1). Consequently, typical clinical features of a DILI by a single drug cannot be obtained from large cohorts as opposed to single DILI case reports or case series that included DILI cases due to a single drug (Table 1). In general, studies with a single DILI case or a few cases are more informative because they provide an exhaustive past medical

Specificities of DILI Case Evaluation
Large study cohorts of RUCAM based DILI cases accumulated many different drugs and provided as expected a global information of the DILI cases due to various drugs without a detailed description of clinical features drug by drug (Table 1). Consequently, typical clinical features of a DILI by a single drug cannot be obtained from large cohorts as opposed to single DILI case reports or case series that included DILI cases due to a single drug (Table 1). In general, studies with a single DILI case or a few cases are more informative because they provide an exhaustive past medical history with clinical details required for a sound case evaluation. In search for typical DILI features by specific drugs, therefore, assistance may be provided by the drug listing (Table 1). In addition, details can be retrieved via the internet, using the search terms drug induced liver injury and the name of the suspected drug, combined with RUCAM or the updated RUCAM.

Worldwide Top Ranking of Drugs Causing DILI
There is concern how best to establish a top ranking of drugs most commonly implicated in DILI [70,74]. A recent study presented a list with top ranking drugs out of overall 3312 DILI cases evaluated by RUCAM (Table 3) [70]. The RUCAM based DILI cases were retrievd from 15 reports by six national databases of DILI registries and three large medical centers worldwide, which provided the DILI cases under consideration. Contributing countries and regions were in alphabetical order China, Germany, Latin America, Iceland, India, Singapore, Spain, Sweden, and the US. It was found that the databases of national registries and large medical centers are the best sources of drugs implicated in DILI cases. There is also the note that presently DILI cases of the LiverTox database are less suitable for clinical or regulatory purposes as presented on its website because many suspected DILI cases were derived from published cases of poor quality, lacking a robust CAM such as RUCAM [70,74]. Consequently, the majority of LiverTox based cases of assumed DILI could previously not be classified as real DILI [74]. To overcome these diagnostic shortcomings, LiverTox attempted a top ranking of drugs by counting the published DILI cases for each individual drug [74]. It was assumed that the degree of causality probability increases with the number of published DILI reports: the higher the case number the higher the probability. This special approach explains the variability of the top listing presented by liverTox [74] as compared to RUCAM based cohorts [70]. Substantially modified from a previous report [70], which provides references for each implicated drug.

Worldwide Publications of HILI Cases Assessed for Causality Using RUCAM
Highlights of liver injury cases have been reported not only for DILI but with increasing frequency also for HILI cases questionable due to lack of a robust CAM [7][8][9]. The problems associated with HILI are specifically addressed in the current analysis, which considers for the first time worldwide HILI cases using RUCAM as a robust algorithm for assessing causality.

Countries and Regions
Authors from many countries around the world reported on cases of HILI in connection with the consumption of various herbs, all published since 1993 (Table 4) [29,37,38,42,48,[100][101][102][103]113,[115][116][117][118]. Specifically considered were patients, who experienced HILI with established causality using RUCAM. Such a table with a comprehensive list of publications over a long period of time will help the search for RUCAM based HILI cases caused by specific herbs or herbal products containing a mixture of several herbs. This list is unique as compared to databases that may have problems providing real HILI cases not confounded by alternative causes or lack of a robust causality assessment.

Hospital and Other Sources
Most RUCAM based HILI cases were provided by authors from university hospitals and their affiliated teaching hospitals with their departments of Hepatology and Gastroenterology, Medicine or Internal Medicine (Table 3). Rare contributors were other departments like those with focus on Emergency Medicine [255], Clinical Pharmacology and Toxicology in Berlin [209], Pharmacology and Toxicology in Hannover [213], Pharmacy in Singapore [238], Physiology and Pharmacology in Rome [219,221], Anatomical, Histological, Forensic and Orthopedic Sciences in Rome [222], Pediatrics in Seoul [234], and among the contributors were even the Neurology and Headache Center in Essen [212] and Spine and Joint Research Institute in Seoul [235].
Other sources providing RUCAM based HILI cases include the Chinese Academy of Medical Sciences in Beijing [195], School of Chinese Materia Medica in Beijing [199,202], Competence Centre for Complementary Medicine and Naturopathy in Munich [211], Biomedical Research and Innovation Platform South African Medical Research Council in Tygerberg [239], United States Pharmacopeia in Rockville [254], and Center of Pharmacovigilance of Florence [218].

Top Ranking Countries
Among the countries presenting RUCAM based HILI cases were on top in descending order China and Korea, followed by Germany, India and the US, whereby the top 5 countries provided most of the HILI cases (Table 5). Authors from these 5 countries contributed together 13,808 HILI cases out of a total 14,029 worldwide HILI cases, corresponding to 98.4%. On the lower part of the list ranked the 4 countries Brazil, Colombia, Switzerland, and Turkey, authors from these low ranking countries provided each one HILI case assessed for causality using RUCAM, corresponding to 4 cases altogether out of a total of 14,029 HILI cases. Authors from the remaining 20 countries with a ranking from 6 down to 14 contributed 217 HILI cases out of overall 14,029 cases corresponding to almost 1.6%.   Phase 1 started after the launch of RUCAM in 1993 [16,47] but without a single published HILI case until 2003 (Figure 3). The lack of published RUCAM based HILI cases during this period might be due to the fact that the value of RUCAM was not yet sufficiently known or to uncertainties whether herbs have the potential to cause liver injury. In addition, the term of herb induced liver injury or its acronym HILI was unknown at that time and therefore not in common use.
During the subsequent phase 2, the number of annual published HILI cases remained small with cases ranging from 2 to 933, considering the years from 2004 until 2016 ( Figure 3). In 2008, there were 108 HILI cases, with 18 Spanish cases published by García-Cortés et al. [117,241] and 90 Korean cases published by Kang et al. [227] and Sohn et al. [228]. During 2016, there was a sharp increase with 933 HILI cases, mostly attributed to 866 cases from China published by Zhu et al. [42]. As a reminder and outlined recently, herb induced liver injury with HILI as its acronym was first introduced and proposed as a specific term in the scientific literature only in 2011 [12]. This may explain retarded publications on HILI cases ( Figure 3). Phase 3 started with low HILI case numbers in 2017 and 2018 (Figure 3), considering that the updated RUCAM applicable also to HILI cases was published only in 2016 [15]. With 11,609 the largest HILI case number was published in 2019 ( Figure 3) as a consequence of the ongoing worldwide use of RUCAM for assessing causality in suspected HILI cases (Table 4). In particular, contributing countries were in alphabetical order Australia [29], Brazil [183], China [48,[196][197][198][199][200][201], Germany [213][214][215], India [217], Italy [222], Korea [103], Spain [115,117,[240][241][242], Switzerland [244], and the US [245][246][247][248][249][250][251][252][253][254]. Most of the 11,619 HILI cases published in 2019 were from China [48,196] and Korea [103], with 6971 cases published by Shen et al. [48], 2019 cases reported by Byeon et al. [103], and 1552 cases provided by Chow et al. [196]. However, until mid 2020 only 57 HILI cases were published (Table 4) [202,203,253,254], suggesting for the whole year 2020 at best 100 cases (Figure 3). Phase 1 started after the launch of RUCAM in 1993 [16,47] but without a single published HILI case until 2003 (Figure 3). The lack of published RUCAM based HILI cases during this period might be due to the fact that the value of RUCAM was not yet sufficiently known or to uncertainties whether herbs have the potential to cause liver injury. In addition, the term of herb induced liver injury or its acronym HILI was unknown at that time and therefore not in common use.

Annual RUCAM Based HILI Publications and Growth Trend
Over the years starting from 1993, when RUCAM was launched [14,57] and until 2019, an upward trend of annual RUCAM based HILI publications can be observed with some dips in between (Figure 4). In 2019, 18 publications were counted and 4 publications until end of June 2020 that were not included ( Figure 4). For the whole year 2020, therefore, at best perhaps 8 publications can be anticipated ( Figure 4). These figures show that a total of 85 publications with RUCAM based HILI cases were reported from 1993 until mid 2020 (Table 2).

Annual RUCAM Based HILI Publications and Growth Trend
Over the years starting from 1993, when RUCAM was launched [14,57] and until 2019, an upward trend of annual RUCAM based HILI publications can be observed with some dips in between (Figure 4). In 2019, 18 publications were counted and 4 publications until end of June 2020 that were not included (Figure 4). For the whole year 2020, therefore, at best perhaps 8 publications can be anticipated (Figure 4). These figures show that a total of 85 publications with RUCAM based HILI cases were reported from 1993 until mid 2020 (Table 2).

Specificities of HILI Cases
Large study cohorts of RUCAM based HILI cases accumulate many different herbs and provide as expected a global information of many HILI cases without a detailed description of clinical features for specific herbs (Table 4). Consequently, studies with a single or a few HILI cases have many advantages because they focus on a single herb or herbal product causing the liver injury and usually provide an exhaustive past medical history with clinical details required for a sound case evaluation. For interested physicians, regulators, and manufacturers, this listing provides individual cases with herbs causing HILI.

Utility of RUCAM
The utility of RUCAM has been confirmed in in many liver injury cases of DILI (Table 1) and HILI (Table 4) published from countries and regions around the world, as outlined in various reports [5,11,[15][16][17][18] and briefly summarized (Table 6). In short, the high qualification of RUCAM as an objective diagnostic algoritm to assess causality in liver injury cases of DILI and HILI is the clue of its increasing use (Figures 1-4). RUCAM is smoothly applied by clinicians or regulators and obviously without problems (Tables 1 and 4). The worldwide use allows data comparison among different countries, a unique condition for multifacetted diseases as DILI and HILI are. RUCAM is also applied in epidemiology studies. Finally and most importantly, each individual DILI and HILI case report contain important details of liver injury cases that may be helpful for physicians in care of patients with suspected DILI and HILI.

Specificities of HILI Cases
Large study cohorts of RUCAM based HILI cases accumulate many different herbs and provide as expected a global information of many HILI cases without a detailed description of clinical features for specific herbs (Table 4). Consequently, studies with a single or a few HILI cases have many advantages because they focus on a single herb or herbal product causing the liver injury and usually provide an exhaustive past medical history with clinical details required for a sound case evaluation. For interested physicians, regulators, and manufacturers, this listing provides individual cases with herbs causing HILI.

Utility of RUCAM
The utility of RUCAM has been confirmed in in many liver injury cases of DILI (Table 1) and HILI (Table 4) published from countries and regions around the world, as outlined in various reports [5,11,[15][16][17][18] and briefly summarized (Table 6). In short, the high qualification of RUCAM as an objective diagnostic algoritm to assess causality in liver injury cases of DILI and HILI is the clue of its increasing use (Figures 1-4). RUCAM is smoothly applied by clinicians or regulators and obviously without problems (Tables 1 and 4). The worldwide use allows data comparison among different countries, a unique condition for multifacetted diseases as DILI and HILI are. RUCAM is also applied in epidemiology studies. Finally and most importantly, each individual DILI and HILI case report contain important details of liver injury cases that may be helpful for physicians in care of patients with suspected DILI and HILI.

Other CAMs
Apart from the objective diagnostic RUCAM algorithm, a few non-RUCAM based CAMs are known, critically discussed elsewhere in detail [5,15]. In short, they are less accurate than RUCAM, not quantitative as not based on specific elements to be scored individually, not specific for liver injury cases, not structured, not validated, or based on individual arbitrary subjective opinions. In fact, other CAMs are still caught up in the pre-RUCAM and pre-AI era [18] and thereby neglecting the use of diagnostic algorithms such as the original RUCAM [14] or the now preferred updated version [18].

Limitation of the Analysis
The current analysis is based on published data of DILI and HILI reports in English, or at least an abstract in English, rather than on unpublished data contained in the original data sets that were not available to the authors of the analysis for re-analysis. Although most of the published DILI and HILI cases provide excellent data, some authors forgot presenting RUCAM based causality gradings or included cases with a possible causality grading in their final evaluations of cases together with a probable or highly probable causality level. Nevertheless, a broad range of different causality gradings was commonly provided in most published cases, respective references allow for detailed information. As being outside the scope of this article, causality gradings for individual reports were not provided (Tables 1 and 5), but some details of 46,266 DILI cases assessed by RUCAM were published earlier [11]. Problematic are study cohorts with inclusion of both DILI and HILI cases, unless both groups were separately evaluated [48]. As expected, not all of the patients were commonly confirmed as being DILI by RUCAM scoring, but the number of published cases remained accurate. For instance, special conditions are evident in the randomized clinical trial of ximelagatran [148]. In this prospective, report, hepatic findings were analyzed in all suspected cases with regard to causal relationship to ximelagatran by using RUCAM, considered as the most reliable tool to assess causality [148]. Applying RUCAM based on ALT thresholds only is insufficient since 92% of the ximelagatran group did not meet this criterion missing then a final robust causality grading, as opposed to 8% of the study group receiving partially high causality gradings. This study reaffirms the utility of RUCAM to identify cases with real DILI cases in cohorts under real world conditions.

Outlook
The perspectives using the updated RUCAM in future DILI and HILI cases are favorable because many authors including those from the US become more familiar with RUCAM and are ready to use this diagnostic algorithm (Tables 1-4), in line with principles of Artificial Intelligence to solve difficult processes [18]. Moreover, as in the US and many other countries RUCAM was successfully used to assess causality in cases of DILI, there is no need to invent another instrument specifically designed for drug development [255]. The issue of overlooked alternative causes remains a clinical problem and was described already in 1999 by Aithal et al. [256] and guided by RUCAM subsequently confirmed [69,257].
Future DILI and HILI studies should adhere on a prospective study design as strongly recommended in the RUCAM updated in 2016 because a retrospective approach may create concern on the validity of the published results due to incomplete information [15]. Neglecting this recommendation and using instead a retrospective design could be problematic [48]. In addition, attempts to lift RUCAM based causality gradings from possible to probable must be resisted [48]. Discouraged is in particular the use of a non-RUCAM based CAM in addition to RUCAM, because such a combination causes uncertainty due to disputable results of causality gradings. It is not recommended to mix in the same cohort patients with DILI or HILI [48] because this situation will complicate a separate evaluation of DILI or HILI features. However, it is clear that in individual cases RUCAM allows for a distinction between a drug and a medicinal herb when causality gradings are different.

Conclusions
The current analysis showed a favorable run of the RUCAM algorithm globally used since its launch in 1993, considering the annually published DILI and HILI cases. Overall 95,885 liver injury cases were published using RUCAM for causality assessment, namely 81,856 iDILI cases and 14,029 HILI cases. The global use of RUCAM assessing causality in cases of DILI and HILI helps compare study results among various countries and facilitates description of typical clinical features, best derived from case reports or small case series. RUCAM solves complex conditions as an algorithm in line with principles of Artificial Intelligence. Top ranking countries providing RUCAM based DILI cases were China, the United States, Germany, Korea, and Italy, whereas most RUCAM based HILI cases were published by authors from China, Korea, Germany, India, and the United States. In term of number of cases published, there is no other causality assessment method that could outperform RUCAM evaluating DILI and HILI cases. This should encourage all the stakeholders involved in DILI and HILI to systematically use RUCAM in order to reinforce their diagnosis and take the right decisions for the benefit of the patients.