An interesting new
study (Harley
2013) has raised the question as to
whether mortality of dialysis patients may be higher when the caseload of their
nephrologist is higher. The authors retrospectively reviewed a cohort of
patients receiving dialysis through facilities of one for-profit provider in an
urban area of California. They found in demographic characteristic–adjusted
analyses that each 50-patient increase in caseload was associated with a 2%
increase in patient mortality risk (hazard ratio, 1.02; 95% confidence
interval, 1.00 to 1.04; P<0.001). Also, patients treated by nephrologists
with the lowest patient mortality rates received higher dialysis doses, had
longer sessions, and received more kidney transplants.
The study
conclusions are limited by the fact that this was one population and the study
lacked important details about severity of illness and other patient level
factors that might be important in terms of mortality. Nevertheless, the study
does raise an important question that should lead to further investigation.
The study comes on
the heels of another study (Kawaguchi
2013) that linked mortality of dialysis patients to the amount of physician
contact they had. That study, using data from the large international Dialysis Outcomes and Practice Patterns Study
(DOPPS), found an inverse correlation between the frequency of
patient-doctor contact and all-cause mortality. They also found that
each 5-minutes-shorter duration of patient-doctor contact was associated
with a 5% higher risk for death, on average, after adjusting for visit
frequency and other covariates. There were also modest inverse associations
between both patient-doctor contact frequency and duration with hospitalization
but not with kidney transplantation.
While there have
been many conditions that have linked physician (or center) experience, usually
measured by volume of cases, to better outcomes, most of those have been
surgical conditions. There have been fewer studies on caseload and mortality
for medical conditions.
But we have seen “J-shaped”
mortality curves in the past. At one time when we were looking a bariatric
surgery mortality rates in New York State we found that mortality rates
declined when a surgeon or center did between 50 and 100 cases. However,
interestingly, there seemed to be an increase in mortality once the 250 case
level was reached. We were unable to tell at that time whether that meant the
surgeons and centers had become too busy or simply that, because of their
experience, they were getting more complex cases. We suspected the latter. We
don’t know whether that observation has held up over the years or not.
Given the
complexities of dealing with all the comorbidities in dialysis patients it would
not be at all surprising that more patient-physician contact might be
associated with better outcomes. But at this point, the observations in these
two studies are merely hypothesis-generating and merit further prospective
studies.
References:
Harley KT, Streja E, Rhee CM, et
al. Nephrologist Caseload and Hemodialysis Patient Survival in an Urban Cohort.
J Am Soc Neprhology 2013; August 8, 201310.1681/ASN.2013020123
http://jasn.asnjournals.org/content/early/2013/08/06/ASN.2013020123.abstract
Kawaguchi T, Karaboyas A, Robinson BM, et al. Associations of frequency and duration of patient-doctor contact in hemodialysis facilities with mortality. J Am Soc Nephrol 2013; July 25, 2013 DOI: 10.1681/ASN.2012080831
http://jasn.asnjournals.org/content/early/2013/07/23/ASN.2012080831.abstract
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