Towards standardized measurement of adverse events in spine surgery: conceptual model and pilot evaluation

Table 8 Etiology categories: Agreement among all four observers for 141 adverse occurrences coded by each reviewer.¹

Etiology Code ²	Category	Kappa	p-value
1	Error in diagnosis	0.52	0.0000
4	Failure to act on results	0.33	0.0000
5	Technical error ³	0.66	0.0000
6	Error in preparation for operation	0.09	0.0064
7	Error in dose or method of use of a drug	0.21	0.0000
8	Avoidable delay in treatment	0.15	0.0000
9	Inappropriate care	0.06	0.0313
10	Failure to provide indicated prophylactic treatment	0.11	0.0007
11	Inadequate monitoring or follow-up	0.05	0.0738
12	Failure in communication ³	0.80	0.0000
13	Equipment failure	0.33	0.0000
14	Other systems failure ³	0.85	0.0000
15	Unclassified error	0.01	0.3453
16	Patient disease, expected risk (no error)	0.26	0.0000
17	Patient non-compliance (no error)	0.00	0.5206
18	Disease unrelated to spine surgery (no error)	0.22	0.0000
16, 17, or 18	No error (16, 17, or 18) ³	0.61	0.0000
----	Combined (for all categories)	0.35	0.0000

¹ Kappa statistic calculated using "kap" command in STATA Version 8 (College Station, TX). Each observation is assumed to be a subject, the number of raters is fixed (4 raters), and more than two outcomes are possible (18 etiology codes).
² None of the 141 adverse occurrences were assigned etiology codes 2 or 3.
³ These categories show substantial or better agreement, with kappa values = 0.61

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