Spending on laboratory testing in BC increased 58.7% between 1996/97 and 2005/06. Many factors, including changes in technology, repeat testing and inappropriate utilization have been proposed as potential factors contributing to the increase in laboratory utilization . One additional explanation for expenditure increases is increased testing consistent with medical practice guidelines for diagnosing and monitoring patients with chronic conditions. We find that there was, indeed such an increase between 1996/97 and 2005/06, but that this explains only about one-third of the total increase, net of population growth and aging. Changes in treatment prevalence were equally important, and unexplained increases in other laboratory tests for people with and without the specific chronic conditions of interest were a large contributing factor.
Several changes in the clinical definition and screening of chronic conditions occurred between 1996/97 and 2005/06. For example, the clinical definition of diabetes shifted from a fasting plasma glucose level of greater than or equal to 7.8 to 7.0 mmol/L [13, 14]. For renal disease, serum creatinine levels of 176.8 μmol/L in men (eGFR of ~40 mL/min/1.73 m2 for a 40 year old man) resulting in referral to a renal team for dialysis assessment, changed to every patient with urine abnormalities and an eGFR <90 mL/min/1.73 m2 receiving immediate further assessment and management [15, 16]. Similarly, the recommended screening guidelines for Type 2 diabetes shifted to begin at age 41 instead of age 46 [13, 14]. There were no major changes in clinical definitions or screening guidelines for osteoarthritis or rheumatoid arthritis and for those conditions we see relatively stable prevalence across age groups over time11. These changes are only two factors that may be driving the increase in treatment prevalence for these chronic conditions, but they are surely significant ones. Once people are diagnosed with a condition, it should be no surprise that associated health care, and particularly guideline-consistent expenditures will follow.
There has also been a trend during this period toward diagnosing “pre-disease” states as part of screening guidelines, and a growing demand from patients for tests of their choosing even if the physician may not consider them beneficial. As previously mentioned, the first screen for diabetes is now recommended at earlier ages regardless of risk factors with a diagnosis of “impaired fasting glucose” as a “pre-diabetic” state at fasting plasma glucose levels of 6.1 mmol/L. These individuals being flagged as “at risk” subsequently require follow up tests until the disease manifests itself . So recommendations for increased population screening at ever earlier ages and the lower threshold for these pre-disease "conditions" that then leads to increased monitoring of individuals with no disease with testing could be another driver of the increase in other laboratory tests [14, 17, 18].
Much has been made of the aging population and its impact on the healthcare system. However, only 5.3% of the growth in laboratory expenditure over this period was actually attributable to a change in the age structure. More is spent on the elderly and this trend has continued between 1996/97 to 2005/06. However, the impact of an increasing treatment prevalence of age-specific chronic conditions, and particularly of an increasing age-specific prevalence of patients with multiple co-morbidities, is far more important.
There are some limitations to this study. The fee-for-service physician data do not include information on services paid for through alternative payment arrangements such as salaries, sessional payments, or contractual arrangements. This does not affect the laboratory payments, which are all by fee-for-service for patients outside of acute care, but may affect our classification of these individuals into the chronic disease categories. In addition, our analysis of chronic conditions was not exhaustive, but rather focused only on those conditions that became the subject of incentive programs for primary care in BC. The “other” laboratory tests, while not guideline-recommended for these specific chronic conditions, may still be appropriate for other conditions. Therefore individuals with other potentially prevalent chronic conditions that were outside the scope of the conditions selected for this study would be classified as ‘no guideline-related chronic condition’, which limits our interpretation of people in this category.