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Test procedural combination and test result grouping

The Hong Kong Reference Framework for Diabetes Care for Adults in Primary Care Settings
(2018) suggests that either FPG or HbA1c tests can be sufficient with added OGTT for
diagnosis of DM (PHO, 2018). Internationally, protocols for DM diagnoses recommend using
combinations of the three above tests. However, due to inherent differences in the respective
tests, there has been substantial debate over the preference of each. For example, while the
OGTT is a diagnostic test, it is also more costly and time-consuming and therefore is
not recommended in the first round of screening. To be most definitive, the
OGTT should be performed to offer an actual clinical diagnosis of
diabetes.

FPG and HbA1c are therefore the recommended candidates for the first round of screening.
The HbA1c test is the most common screening test due to its low cost and ease of
administration, given that it can be stored at ambient temperatures and administered at any
time of the day without requiring fasting random blood samples (Lim et al., 2018). However,
the HbA1c test’s measurement can be affected by a variety of genetic, haematologic and
illness-related factors (FHB, 2018; Gallagher et al., 2009). Alternatively, the FPG test can be
administered through measurement of fasting blood glucose levels and therefore difficult to
achieve on a mass population screening level. Furthermore, due to conflicting evidence
internationally on the test performance of FPG and HbA1c, there remains conflict over the
use of only one of the two tests alone to assess pre-diabetes or DM diagnosis (Appendix R).
(Barry et al., 2017)

In view of this, our prospective screening programme proposes aligning with the
recommendation stipulated under the Hong Kong Reference Framework for Diabetes Care
for Adults in Primary Care Settings (2018) with the added component of combining the FPG
and HbA1c tests. In combining the FPG and HbA1c tests, we propose that we may partly
overcome the associated inaccuracies within each screening test. Additionally, we may be
able to better estimate the cost to improve diagnosis accuracy and provide the necessary
treatment protocols to patients.

Therefore, the screening programme shall consist of at least one round of
screening: with one mandatory round of combined FPG & HbA1c tests,
followed by either a repeat of both or both tests in addition to OGTT
if patients fall into the thresholds for either DM or prediabetes. All calculations for the
economic projection model will therefore follow the current FHB protocol for prediabetes or
DM diagnosis with the additional component of combining FPG + HbA1c tests.

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