Table 1.

Characteristics

Patients, N	4964
Age (years) at initial biopsy, median (IQR)	7·85 (3·25–11·98)
<6, n (%)	1982 (39·9%)
6–11, n (%)	1743 (35·1%)
12–17, n (%)	1236 (24·9%)
Missing values, n (%)	3 (0·1%)
M/F ratio (% males)	2551/2413 (51·4%)
Time span of the collection of data, range	Jan. 1988		Dec. 2007
Period, n (%)
1988–1993	941		(19·0%)
1994–1998	1086		(21·9%)
1999–2003	1329		(26·8%)
2004–2007	1608		(32·4%)
Without follow-up, n (%)	4042		(81·4%)
Repeated biopsy, n (%)
1	586	}922	(11·8%)	}18.6%
2	153		(3·1%)
3	82		(1·7%)
4	46		(0·9%)
5	18		(0·4%)
6	12		(0·2%)
⩾7	25		(0·5%)
Non-European, n (%)	3489		(70·3%)

IQR, Interquartile range.