Correction: An Assessment of the Methodological Quality of Published Network Meta-Analyses: A Systematic Review.

[This corrects the article DOI: 10.1371/journal.pone.0121715.].

In the second paragraph of the Results the sentence describing the number of studies receiving non-profit or no support should read “The majority of studies adopted a Bayesian framework (n = 214, 67%) and either received non-profit or no support (n = 217, 69%).”

In the final paragraph of the Results the percentage of studies with a closed loop is incorrect. The correct sentence should read “Among studies with a closed loop, i.e., three or more included treatments had been compared in head-to-head trials, 31% did not report the consistency of direct and indirect evidence.”

Under Publication Date the p value for 62% versus 79% should read (62% versus 79%, p = 0.0005).

Under Source of Financial Support the p value for 49% versus 28% in the first paragraph should read (49% versus 28%, p = 0.0003).

Under Source of Financial Support the second paragraph should read “Industry-supported studies more often used a Bayesian framework (77% versus 63%, p = 0.0191), and adjusted for study covariates (38% versus 25%, p = 0.0205); however, they less often performed a risk of bias assessment of included studies (54% versus 77%, p∠0.0001), and, for closed loop studies, less often compared the consistency of direct and indirect evidence (39% versus 79%, p∠0.0001).”

In the Discussion the third paragraph should read “An interesting finding is that industry-sponsored studies more often used a Bayesian framework”

Fig 1 is incorrect in the published article. Please see the correct Fig 1 here.

Fig 1

Identification of network meta-analyses included in review.

There are errors in Table 1 and Table 2 of the published article. Please see the correct tables here.

Table 1

Frequency of network meta-analyses (n = 318) by year, indication, and country

Year study published†	n
1997	1 (0.3%)
2003	3 (0.9%)
2004	1 (0.3%)
2006	3 (0.9%)
2007	3 (0.9%)
2008	9 (2.8%)
2009	16 (5.0%)
2010	21 (6.9%)
2011	44 (13.8%)
2012	66 (20.4%)
2013	78 (24.5%)
2014 (through July 31st)	73 (23.0%)
International Statistical Classification of Diseases (ICD) disease categories	n
Blood Disease	3 (0.9%)
Circulatory System	64 (20.1%)
Digestive System	13 (4.1%)
Endocrine, Nutritional, Metabolic, and Immunity	28 (8.8%)
Genitourinary System	7 (2.2%)
Infectious and Parasite Disease	14 (4.4%)
Mental and Behavioral Disorder	13 (4.1%)
Musculoskeletal System and Connective Tissue	45 (14.2%)
Neoplasm	39 (12.3%)
Nervous System and Sensory Organs	33 (10.4%)
Respiratory System	20 (6.3%)
Skin and Subcutaneous Tissues	9 (2.8%)
Other	30 (9.4%)
Country	n
USA	81 (25.5%)
UK	79 (24.8%)
Canada	28 (8.8%)
Italy	21 (6.6%)
China	16 (5.0%)
France	14 (4.4%)
The Netherlands	10 (3.1%)
Germany	8 (2.5%)
Brazil	6 (1.9%)
Switzerland	6 (1.9%)
Taiwan	6 (1.9%)
Greece	5 (1.6%)
Spain	4 (1.3%)
Other	34 (10.7%)
Type of pharmaceutical intervention included	n
Multiple pharmaceuticals compared	304 (95.6%)
Study included a non pharmaceutical treatment (e.g., surgery, exercise, counselling, etc)	30 (9.4%)
Different strengths of the same pharmaceutical compared (e.g., simvastatin 20mg vs. 40mg)	82 (25.8%)
Treatments in the same drug class grouped together as a comparator (e.g., beta-blockers, or statins)	75 (23.6%)
Multiple modes of administration of a drug compared (e.g., oral, sublingual, intramuscular, etc)	10 (3.1%)

† We limited our literature search to studies published in the medical literature. We did not include NMAs submitted to national health technology assessment agencies unless also published in the Ovid-MEDLINE database. * ‘Other countries’ includes Greece, Ireland, Singapore, Australia, Cameroon, Denmark, Finland, Hong Kong, Korea, Norway, Poland, and Portugal.

Table 2

Assessment of network meta-analysis study characteristics

Assessment criteria	All studies (n = 318)	Journal quality (n = 301)*			Date of study publication (n = 318)			Source of study support (n = 315)**
		Low impact factor (<3.534) (n = 147)	High impact factor (≥3.534) (n = 154)	p-value	Older studies (published prior to 2013) (n = 167)	Recent studies (2013, 2014) (n = 151)	p-value	Industry support (n = 98)	Non-Industry support/ no support (n = 217)	p-value
General study characteristics
Number of treatments compared	6.3 (±6.4)	6.8 (±8.5)	6.0 (±3.9)	0.3136	6.0 (±4.2)	6.7 (±8.2)	0.3816	5.9 (±3.6)	6.5 (±7.3)	0.446
Total number of studies	32.9 (±45.5)	28.3 (±38.6)	36.5 (±46.9)	0.0992	30.5 (±50.2)	35.5 (±50.2)	0.3341	22.7 (±29.4)	37.4 (±50.5)	0.0079
Total number of patients	26875 (±65936)	21938 (±46061)	33292 (±82859)	0.1549	23711 (±49899)	30460 (±80375)	0.3732	10945 (±13183)	33864 (±77635)	0.005
HTA region (UK, AUS and Canada)†	110 (35%)	50 (34%)	56 (36%)	0.6709	68 (41%)	42 (28%)	0.0156	48 (49%)	62 (28%)	0.0003
Journal impact factor	5.5 (±6.2)	NA	NA	NA	5.8 (±6.5)	5.2 (±5.9)	0.3791	3.1 (±1.7)	6.5 (±7.1)	<0.0001
Study method
Bayesian framework	214 (67%)	91 (62%)	109 (71%)	0.1038	106 (63%)	108 (72%)	0.1273	75 (77%)	139 (63%)	0.0191
Risk of bias assessment of included studies	223 (70%)	100 (68%)	111 (72%)	0.4446	103 (62%)	120 (79%)	0.0005	53 (54%)	170 (77%)	<0.0001
Adjustment for covariates	92 (29%)	35 (24%)	51 (33%)	0.0744	54 (32%)	38 (25%)	0.1601	37 (38%)	55 (25%)	0.0205
Random effects model***	221 (70%)	98 (67%)	114 (75%)	0.1609	116 (69%)	106 (71%)	0.7453	67 (68%)	155 (71%)	0.6243
Assessment of model fit	127 (40%)	53 (36%)	70 (45%)	0.0979	69 (41%)	58 (38%)	0.5985	46 (47%)	81 (37%)	0.0894
Sensitivity analysis	179 (56%)	73 (50%)	96 (62%)	0.0267	88 (53%)	91 (60%)	0.1752	57 (58%)	122 (58%)	0.6542
Consistency of direct and indirect evidence reported**** (closed loop studies only, n = 167)	116 (69%)	39 (57%)	73 (79%)	0.0017	57 (66%)	59 (73%)	0.3606	16 (39%)	100 (79%)	<0.0001
Study transparency and reproducibility
Search terms reported	254 (80%)	112 (76%)	129 (84%)	0.1007	129 (77%)	125 (83%)	0.2201	61 (62%)	193 (88%)	<0.0001
Network diagram	194 (61%)	85 (58%)	101 (66%)	0.1671	103 (62%)	91 (60%)	0.7974	62 (63%)	132 (60%)	0.5829
Extracted data from contributing clinical studies	206 (65%)	87 (60%)	106 (69%)	0.0955	116 (69%)	91 (60%)	0.1011	58 (60%)	149 (68%)	0.1726
Table of key clinical study characteristics	286 (90%)	128 (87%)	141 (92%)	0.2084	145 (87%)	141 (93%)	0.0527	89 (91%)	197 (90%)	0.729
Model code (Bayesian framework only, n = 214)	35 (16%)	9 (6%)	24 (16%)	0.0085	24 (14%)	11 (7%)	0.0439	8 (8%)	27 (12%)	0.2811
Presentation of study findings
Full matrix of head-to-head comparisons	203 (64%)	84 (57%)	108 (70%)	0.0191	110 (66%)	93 (62%)	0.4294	44 (45%)	159 (73%)	<0.0001
Reported probability of being best (Bayesian framework only, n = 214)	87 (41%)	32 (22%)	51 (33%)	0.0277	41 (25%)	46 (30%)	0.2389	25 (26%)	62 (28%)	0.623
Ranking of included treatments (Bayesian framework only, n = 214)	67 (31%)	26 (18%)	40 (26%)	0.0829	29 (17%)	39 (26%)	0.0664	11 (11%)	56 (26%)	0.0031

† Regions in which submissions to HTA agencies generally require a NMA

* 17 studies published in journals with no associated impact factor

** 3 studies for which source of study support was unclear

*** 77 studies reported both fixed and random effects models, 38 studies did not report models used

**** Consistency only reported for studies with a closed loop