Table 2

Risk of spinal hematoma when no such complication has occurred is calculated according to the number of lumbar punctures (LPs) in each category of thrombocytopenia

Platelet count (×10⁹/L)	LPs (n)*	Upper risk limit of one-sided 95% CI	’Best’ estimate of risk
1–10	74	0.0405	0.0054
11–20	298	0.0100	0.0013
21–30	402	0.0075	0.0010
31–40	391	0.0077	0.0010
41–50	444	0.0068	0.0009
51–100	1747	0.0017	0.0002

*The column under ‘LPs (n)’ represents the total number of LPs from the eight series referenced in table 1. Where the category ranges are wider than those in this table (refs. 4,8,10,11), the numbers are roughly equally subdivided into the ranges for entry into this table.