National Bowel Cancer Audit Report 2011 - HQIP

Results
6.1. Case ascertainment and linkage in NBCA and HES
Of the 29,577 new diagnoses of bowel cancer ascertained
in HES, 72 per cent were linked to NBCA on NHS number.
82 per cent of the 26,251 cases ascertained in England in
NBCA were linked to a patient in HES. See Table 6.1 below.
The patients identified in HES who were unlinked to NBCA
were spread fairly evenly across all trusts. Note that some
of the cases unlinked between NBCA and HES could be
unlinked due to linkage errors. This would mean that some
of the 8,143 cases ascertained in HES but unlinked to NBCA
were the same patients as the 4,817 cases ascertained in
NBCA but unlinked to HES. Depending on the extent to
which linkage is a problem, the percentage of all cases
ascertained in HES that were not captured in NBCA could
be as low as 10 per cent or as high as 30 per cent.
Table 6.1
Total cases identified by HES and NBCA, according to whether or not they are linked between the two data sources.
Case ascertained in NBCA
Case ascertained in HES Yes No Total
Yes 21,434 8,143 29,577
No 4,817 N/A
Total 26,251
6.2. Characteristics of patients not ascertained in NBCA
compared to those ascertained
Patients undergoing major surgery were much more
likely to be captured in NBCA (Table 6.2). 73 per cent
of cases ascertained in NBCA had major surgery according
to HES, compared to only 46 per cent of cases not
ascertained in NBCA.
Table 6.2
29,577 patients ascertained in HES. Percentage undergoing major surgery according to HES, in those ascertained and not ascertained in NBCA
Major surgery according
to HES
Ascertained in NBCA
Yes % No % Overall % P for difference
Yes 15,534 72.5 3,713 45.6 19,247 65.1 P