The effect of specialist care within the first year on subsequent
outcomes in 24 232 adults with new-onset diabetes mellitus:
population-based cohort study
F A McAlister, S R Majumdar, D T Eurich, J A Johnson
............................................................... ............................................................... .....
See end of article for
Dr S R Majumdar, 2E307
WMC, University of Alberta
Hospital, 8440 112 Street,
Edmonton, Alberta, Canada
T6G 2R7; me2.majumdar@
24 September 2006
Qual Saf Health Care 2007;16:6–11. doi: 10.1136/qshc.2006.018648
Background: Although specialty care has been shown to improve short-term outcomes in patients hospitalised
with acute medical conditions, its effect on patients with chronic conditions treated in the ambulatory care
setting is less clear.
Objective: To examine whether specialty care (ie, consultative care provided by an endocrinologist or a
general internist in concert with a patient’s primary care doctor) within the first year of diagnosis is associated
with improved outcomes after the first year for adults with diabetes mellitus treated as outpatients.
Design: Population-based cohort study using linked administrative data.
Setting: The province of Saskatchewan, Canada.
Sample: 24 232 adults newly diagnosed with diabetes mellitus between 1991 and 2001.
Method: The primary outcome was all-cause mortality. Analyses used multivariate Cox proportional hazards
models with time-dependent covariates, propensity scores and case mix variables (demographic, disease
severity and comorbidities). In addition, restriction analyses examined the effect of specialist care in low-risk
Results: The median age of patients was 61 years, and over a mean follow-up of 4.9 years 2932 (12%) died.
Patients receiving specialty care were younger, had a greater burden of comorbidities, and visited doctors
more often before and after their diabetes diagnosis (all p(0.001). Compared with patients seen by primary
care doctors alone, patients seen by specialists and primary care doctors were more likely to receive
recommended treatments (all p(0.001), but were more likely to die (13.1% v 11.7%, adjusted hazard ratio
(HR) 1.17, 95% confidence interval (CI) 1.08 to 1.27). This association persisted even in patients without
comorbidities or target organ damage (adjusted HR 1.16, 95% CI 1.01 to 1.34).
Conclusion: Specialty care was associated with better disease-specific process measures but not improved
survival in adults with diabetes cared for in ambulatory care settings.
primary care doctors, the literature asserting improved out-
comes with specialist-based care is based largely on short-term
outcomes in patients hospitalised with acute myocardial
infarction, heart failure, stroke or asthma.1However, for
chronic conditions treated largely in the ambulatory care
setting, such as diabetes mellitus, the evidence is less definitive.
Although several studies have reported that specialists are
more likely to carry out recommended tests2–8or to increase
hypoglycaemic treatment,9 10only one of the seven studies that
have examined atherosclerotic risk factor control found
significant benefits from specialist care after adjustment for
case-mix and selection bias related to referral patterns.2 3 10–14
Although one study reported a lower rate of microvascular
complications in patients treated by specialists, this difference
disappeared after adjustment for differences in case-mix and
baseline physiological measures.12All of these studies are
limited; they have small numbers, are restricted to highly
selected patients, have short durations of follow-up, or focus on
However, focusing on disease-specific outcomes does not
consider the possibility that specialist-based care may improve
processes and outcomes related to the target condition, but not
for other conditions. Of the two studies that investigated all-
cause mortality in people with diabetes treated by specialists
compared with those treated by primary care doctors, one
lthough studies often report that specialists are more
knowledgeable and more likely to use proved efficacious
treatments within their area of expertise than are
found no difference in 424 patients,13and although the other
reported lower mortality in patients attending a diabetes clinic,
their analyses were not adjusted for comorbidities.15
Thus, we designed this study to examine the relationship
between the doctors providing ambulatory care and long-term
outcomes in adults with new-onset type 2 diabetes mellitus.
We used the linked databases of Saskatchewan Health (drug,
doctors’ claim, hospitalisations and vital statistics), which have
been described in detail elsewhere,16to examine the relation-
ship between the treating doctor and outcome in patients with
diabetes mellitus. These databases are comprehensive and of
high quality, have been used in numerous epidemiological
studies,16and, unlike similar databases in other jurisdictions,
the prescription drug data are not restricted by age.
The Canadian healthcare system is publicly funded and
provides universal access to doctor and hospital services.
Institutional approval for the study was obtained from the
health research ethics board of the University of Alberta.
Of the 64 079 Saskatchewan residents with diabetes (using a
definition previously validated for Canadian administrative
databases)17who received care between 1991 and 2001, we
Abbreviation: ACE, antiotensin-converting enzyme
excluded those without drug prescription data (n=4416
registered Indians, inmates and federal employees), those with
diabetes when our study began in 1991 (n=20 227), and those
who did not see a doctor again in the first year after diagnosis
(n=592). To limit our sample to patients with type 2 diabetes,
we excluded those who were diagnosed with diabetes before
20 years of age (n=2683) and those who were treated
exclusively with insulin from the time of diagnosis (n=637).
To limit the possibility that our results would be skewed by
early clinical events occurring before outpatient care could have
any effect, we excluded those patients who were hospitalised
within the first year of diagnosis (n=11 292).
Thus, our study sample consisted of 24 232 adults with a new
diagnosis of diabetes after 1991, and who had at least 1 year of
continuous coverage under the Saskatchewan health plan.
Exposure to specialty care
Data on doctors’ claims were used to define two groups: those
patients who had been seen as an outpatient at least once by a
general internist or an endocrinologist in the first year after
diagnosis of diabetes were defined as having received ‘‘specialty
care’’ and those who had been seen by family doctors alone
were defined as having received ‘‘primary care’’. It should be
noted that over 99% of the patients who received ‘‘specialty
care’’ were still followed up by their primary care doctor on an
In Canada, as in the UK, patients cannot self-refer themselves
to general internists or endocrinologists and neither of these
specialist groups provides ongoing primary care. Unlike the USA,
general internists act as specialists within the Canadian
healthcare system by providing consultative care—indeed, of
the 119 medical specialists accepting referrals of patients with
diabetes in Saskatchewan, 118 are general internists (College of
Physicians and Surgeons of Saskatchewan physician registry,
searched 8 Aug 2006). Although primary care doctors in Canada
can practice independently after only 1–2 years of postgraduate
training, both general internists and endocrinologists have to
complete a minimum of 4 years of hospital-based postgraduate
training (the first 3 years of which are common between these
specialty streams) and pass written and oral examinations in
internal medicine of the Royal College of Physicians and
Surgeons of Canada.
Our primary outcome was all-cause mortality, and secondary
outcomes included new prescriptions for drugs specific for
diabetes and new prescriptions for cardiovascular drugs
recommended for adult patients with diabetes (statins, anti-
platelet agents and angiotensin-converting enzyme (ACE)
inhibitors).18All patients were prospectively followed up until
death, emigration from Saskatchewan, or 31 December 2001,
whichever came first.
We used x2and Kruskal–Wallis tests to compare baseline
characteristics across groups, Kaplan–Meier analysis to exam-
ine unadjusted survival patterns across study groups, and Cox
proportional hazards regression models to assess the indepen-
dent relationship between the type of treating doctor and
outcomes. Potential confounding variables included as fixed
covariates in all multivariate models were age, sex, rural/urban
residence, total visits to doctor before diagnosis of diabetes,
comorbidities at baseline and the modified Chronic Disease
Score.19–22The Chronic Disease Score provides an indication of
the burden of comorbidity by identifying specific drug treat-
ments prescribed during the follow-up period, and has been
shown to predict resource use, hospitalisation and mortality.19–23
To adjust for potential selection bias (confounding by indica-
tion), we calculated a propensity score for specialist care using
standard methods (logistic regression modelling exposure to
specialist against potential confounding variables, but without
considering the outcomes) and included this as a fixed
covariate in all multivariate models.24Finally, to control for
survivor bias, we used time-dependent variables to adjust for
the cumulative number of visits to a doctor after diagnosis of
diabetes. Proportionality assumptions for the Cox model were
tested with both the goodness-of-fit and log-minus-log tests
and met for all analyses. All first-order interaction terms were
tested in these models; as none had p,0.20, none were
included in our final models.
By using a previously published approach to minimise the effect
of confounding by unmeasured comorbidities,25we examined
the effect of specialty care in the healthiest subgroups (patients
without documented comorbidities or atherosclerotic target
organ damage)—we hypothesised that any differences in
outcomes between different ambulatory care physicians should
be least subject to confounding in this group.
In three sensitivity analyses we redefined ‘‘specialty care’’ on
the basis of: (1) threshold (with only those who had at least
three outpatient visits with a specialist in the first year after
diagnosis of diabetes being classified as receiving specialty
care); (2) dosage (defined as the percentage of total outpatient
visits that were with a specialist, and grouped into ,25%, 25–
50% and .50%); and (3) timing (with only those referred
within the first 6 months after diagnosis compared with those
who were referred later in the first year).
The median age at diagnosis of diabetes was 61 years. Patients
referred to a specialist by their primary care doctor in the first
year after diagnosis of diabetes were younger, more likely to be
men, more likely to be from an urban setting, had a greater
burden of comorbidities and visited doctors more often than
patients seen solely by primary care doctors (table 1).
Of patients receiving specialty care, 2134 (31%) had >3
specialist visits within the first year and specialist visits
accounted for more than half of the total outpatient visits in
that first year in 706 (10%) patients. Only 114 (0.5%) patients
were treated solely by a specialist after diagnosis of diabetes—
all other patients in the specialty care group were also seen on
an ongoing basis by their primary care doctor (indeed, specialty
care patients averaged almost two extra visits to their primary
care physician in the first year after diagnosis; table 1).
Use of diabetes-specific treatments
Over the mean follow-up of 4.9 years in this study, patients
receiving specialty care were more likely to be started on insulin
(996/6842 (15%) v 1672/17 390 (10%), p,0.001) and were more
likely to be prescribed >2 oral hypoglycaemic agents (1935/
6842 (28%) v 4488/17 390 (26%), p,0.001) than primary care
patients. The association between increased insulin use and
specialty care was maintained in all adjusted analyses (fig 1).
Furthermore, specialty care patients who were started on
insulin were started significantly sooner than primary care
patients (mean 4.5 v 4.7 years, p,0.001).
Use of cardiovascular drugs
Specialty care patients were more likely than primary care
patients to be started on cardiovascular agents recommended for
adult patients with diabetes (p,0.001): 21% v 15% for statins,
19% v 14% for antiplatelet agents, 41% v 38% for ACE inhibitors
and 5% v 3% for all three agents. The association between
Specialist care in diabetes7
cardiovascular drug use and specialty care was maintained even
after adjustment for all covariates including time-dependent
covariates and propensity scores (adjusted hazard ratio (HR)
1.19, 95% confidence interval (CI) 1.01 to 1.40).
Subgroup analyses confirmed that patients with coronary
artery disease at baseline were more likely to be prescribed
statins (28% v 17%, p,0.001) and those with heart failure at
baseline were more likely to be prescribed an ACE inhibitor
(41% v 38%, p,0.001) if they received specialty care.
Over 5 years of follow-up, all-cause mortality was higher in
specialty care patients (893/6842, 13.1%) than patients cared for
solely by primary care doctors (2039/17 390, 11.7%; fig 2). The
unadjusted mortality risk in specialty care patients was 1.15 (95%
CI 1.07 to 1.25) compared with primary care patients; the
mortality excess in specialty care patients remained significant in
models adjusting for case mix, propensity score and time-varying
covariates (adjusted HR 1.17, 95% CI 1.08 to 1.27, fig 3). In
addition, this association persisted in all low-risk subgroups
(fig 4) regardless of whether the definition of specialty care was
restrictedtoonlythose patients who saw a specialistat leastthree
times per year (adjusted HR 1.34, 95% CI 1.18 to 1.52) or only
those who saw a specialist within the first 6 months of diagnosis
(adjusted HR 1.32, 95% CI 1.19 to 1.47). There was also a dose–
response gradient; compared with those patients who had all of
their outpatientvisitswitha primary caredoctor, the adjustedHR
was 1.09 (95% CI 0.996 to 1.20) for those receiving ,25% of their
outpatient care from a specialist, 1.14 (95% CI 0.97 to 1.35) for
those receiving 25–50% of their outpatient care from a specialist,
and 2.04 (95% CI 1.69 to 2.45) for those who had .50% of their
outpatient visits with a specialist.
In our study of adults newly diagnosed with diabetes in a
publicly funded healthcare system with universal access, those
follow-up period); FP, family physician.
Use of insulin. CDS, Chronic Disease Score (an indication of burden of comorbidity based on number and type of drugs prescribed during the
Characteristics of patients at baseline, by exposure groups
Age, years (mean (SD))
Men, n (%)
Practice setting, n (%)
Total visits to a doctor in the year before
diagnosis of diabetes (mean (SD))
Comorbidities at baseline, n (%)
Coronary artery disease
Resource use within the first year of diabetes diagnosis, (mean (SD))
Primary care visits within the 1 year
Specialist visits within the 1 year
8 McAlister, Majumdar, Eurich, et al
referred for specialist assessment were younger, more likely to
be men, more often from large urban centres, and had a higher
burden of comorbidities than patients cared for solely by
primary care doctors. Patients receiving specialty care were seen
more often (both by their primary care physician and by all
doctors), were more likely to be treated with insulin and
combination oral hypoglycaemic agents, and more likely to
receive treatment proved efficacious in preventing atherosclero-
tic complications. Despite these advantages, patients receiving
specialty care did not exhibit improved survival, even after
adjustment for covariates and even in subgroups without
comorbidities or target organ damage at baseline.
Although our findings may merely reflect confounding by
indication (ie, specialists are only referred sicker patients with
more comorbidities or more severe disease who are more likely
to die), we adjusted for all available prognostic factors,
restricted our analyses to incident cases of diabetes, dealt with
time-varying exposures that could lead to survivor bias, used
propensity scores to minimise selection bias related to specialist
referral, performed sensitivity analyses to examine different
definitions for specialty care, and attempted to minimise
confounding by performing fully adjusted analyses in low-risk
patient subgroups without comorbidities or target organ
damage. Importantly, the magnitude of the association
between specialty care and mortality was not appreciably
reduced with any of these adjustments (and in some patients
was even increased), and the association was consistent in
magnitude and directionality across all examined subgroups.
An unmeasured confounder would have had to be three times
more common among patients treated in primary care and
associated with an approximate 3% absolute mortality benefit
to appreciably alter our results.
Given the absence of data supporting the converse viewpoint
that specialty care for patients with diabetes improves the
mortality, perhaps the assumption that specialty care is better
for all patients, all conditions, and in all circumstances deserves
re-examination. Several recent studies have documented that
although healthcare expenditures are greater in regions (or
healthcare delivery systems) with higher-intensity specialist-
driven practice patterns compared with regions or systems
exhibiting more conservative primary-care-based practice pat-
terns, quality of care and outcomes are not appreciably better
(and, for some preventive services such as influenza vaccination
and cancer screening, in fact worse).26–30To paraphrase Elliott
Fisher, ‘‘more is not always better’’.31 32Is it plausible that
specialty care for people with type 2 diabetes might be
associated with poorer outcomes? Certainly, the fragmentation
of care that can occur when more than one doctor becomes
involved with a patient may negatively affect the outcomes (for
instance, one can imagine situations in which both doctors may
assume that the other is dealing with non-diabetes-related
issues such as flu vaccinations or cancer screening).33Indeed, a
study on elderly Canadians showed that patients who saw more
than one doctor were at increased risk for receiving an
inappropriate drug combination.34In our study, we did find a
dose–response gradient in the association between specialty
care and mortality; within the specialty care group, those
type of drugs prescribed during the follow-up period); FP, family physician.
All-cause mortality .5 years, crude and adjusted. CDS, Chronic Disease Score (an indication of burden of comorbidity based on number and
12.00 10.008.00 6.00 4.00 2.000.00
Time followed up (years)
Proportional hazards survival rate
or primary care doctors (crude mortality).
Kaplan–Meier graph of survival in patients treated by specialists
Specialist care in diabetes9
patients who received a greater percentage of their ambulatory
care from a specialist had poorer outcomes than those who
received most of their outpatient care from a primary care
doctor. Secondly, although specialists are more likely to order
tests and treatments for their target condition, they are also less
likely to investigate or treat other conditions outside their area
of specialty.7 35 36Thus, for a condition such as diabetes, in
which 5-year mortality is driven more by cardiovascular than
diabetes-related events, the benefits of a disease-specific
specialist may be less than for other conditions (such as heart
failure) in which the target condition accounts for the bulk of
subsequent mortality within a relatively short timeframe.37
Finally, perhaps doctors’ specialty is less important than their
experience with the target condition; for a common condition
such as diabetes, experienced primary care doctors will have
dealt with more patients than junior specialists.
Although our study includes a large, representative and popula-
tion-based sample of all adults with newly diagnosed diabetes
and all doctors in Saskatchewan, followed up for a long period of
time, and our analyses were adjusted for covariates known to
affect outcomes in patients with diabetes, there are some
limitations to our study. Firstly, we did not have data on
physiological parameters such as blood pressure, cholesterol
levels or glycaemic control in our study subjects; thus, we cannot
say whether specialty care patients had poorer outcomes because
their metabolic parameters were less optimal. In a related vein,
we do not have data on severity of comorbidities and thus can
only adjust for the presence or absence of the comorbidities listed
in table 1 in our analyses (although we did include in our
adjustments the Chronic Disease Score, which has been shown to
perform well as a proxy for disease severity).20–23Secondly, we
focused on all-cause mortality, and there may well be non-
mortality benefits arising from specialty care that our study was
unable to capture. Thirdly, as over 99% of our patients who
received specialty care continued to be followed up by their
primary care doctor, our study does not provide information on
the effect of pure specialty care in patients with diabetes (eg, a
system whereby all patients with diabetes are referred to, and
subsequently followed up indefinitely by, a specialised diabetes
service without involvement of their primary care doctor).
Although such a system has been shown to be efficacious for
patients with heart failure deemed to be at high risk for
hospitalisation,38the practicality of such a system for diabetes
(which is far more prevalent and associated with a much greater
survival time) remains to be investigated. Thus, our study
highlights the need for ongoing evaluation of different models
of care provision, and in particular the need for high-quality
evidence evaluating the effect of specialty care for chronic
conditions dealt with in ambulatory care settings (such as
diabetes mellitus) with attention to health-related quality of life
as well as measures of health resource use, morbidity and
In conclusion, despite the common assumption that specialty
care for patients with chronic conditions invariably improves
the quality of their care and their prognosis, our study suggests
that specialty care can improve disease-specific process mea-
sures without necessarily improving overall health outcomes.
Although we showed a robust association between receiving
specialty care and poorer outcomes, which persisted through all
adjustments and sensitivity analyses, our study is merely
observational and we are certainly not suggesting that
specialists cause adverse outcomes. However, we believe that
our study should raise the awareness that specialty care may
not necessarily improve the clinical outcomes for all conditions.
We thank Dr Richard Lewanczuk for his comments on our manuscript.
This study is based on non-identifiable data provided by the
Saskatchewan Department of Health. The interpretation and conclu-
sions contained herein do not necessarily represent those of the
Government of Saskatchewan or the Saskatchewan Department of
F A McAlister, S R Majumdar, D T Eurich, J A Johnson, Department of
Medicine, University of Alberta, Edmonton, Alberta, Canada
Funding: DTE holds a full-time studentship in health research from the
Alberta Heritage Foundation for Medical Research (AHFMR). SRM and
FAM receive salary from the Canadian Institutes of Health Research (CIHR)
and the AHFMR. FAM holds the University of Alberta/Merck Frosst/Aventis
Adjusted analyses for 5-year all-cause mortality in low-risk subgroups. CAD, coronary artery disease; renal/retinal/neuro disease, diabetic
10 McAlister, Majumdar, Eurich, et al
Chair in patient health management. JAJ is a health scholar with the Download full-text
AHFMR and holds a Canada Research Chair in diabetes health outcomes.
JAJ is the chairman of a New Emerging Team (NET) grant to the Alliance
for Canadian Health Outcomes Research in Diabetes (ACHORD). The
ACHORD NET grant is sponsored by the Canadian Diabetes Association,
the Heart and Stroke Foundation of Canada, The Kidney Foundation of
Canada, the CIHR—Institute of Nutrition, Metabolism and Diabetes, and
the CIHR—Institute of Circulatory and Respiratory Health. None of these
sponsoring agencies had any input into the design, conduct or reporting of
Competing interests: None.
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