Table 3 Distribution of CFTR mutation classes in the patient groups: classes I, II and III are usually associated with a “severe” phenotype whereas classes IV and V are usually associated with a “mild” phenotype

Mutation classes(mutation 1/mutation 2)	CF-PS	CFTR dysfunction	CF unlikely
S/S	3 (3)	2 (3)	0
S/M	39 (38)	34 (58)	0
S/?	18 (17)	5 (8)	0
S/??	16 (16)	7 (12)	4 (9)
M/M	1 (1)	1 (2)	0
M/?	3 (3)	2 (3)	0
M/??	7 (7)	1 (2)	1 (2)
?/?	5 (5)	1 (2)	1 (2)
??/??	10 (10)	5 (8)	39 (87)
?/??	1 (1)	0	0
Missing mutation analysis	0	1 (2)	1 (2)
Total n (% of group)	103 (100)	59 (100)	46 (100)

S, severe (class I–III); M, mild (class IV and V); ?, unknown class; ??, no mutation found.
Data are presented as absolute number (percentage).
CF-PS, patients with a sweat chloride value above 60 mmol/l and pancreatic sufficiency; CFTR dysfunction, patients with an intermediate sweat chloride value (30–60 mmol/l) plus two CFTR mutations detected and/or abnormal nasal potential difference; CF unlikely, patients having an intermediate sweat chloride value but no proof of CFTR dysfunction.