Thinking of having a higher predictive power for your first-stage model in propensity score analysis? Think again

Relationship of early postoperative perceived leg length discrepancy to the progression of osteoarthritis in the contralateral hip after unilateral total hip arthroplasty—a retrospective cohort study using propensity score matching

[Purpose] This study aimed to identify the relationship between the early postoperative perceived leg length discrepancy after unilateral total hip arthroplasty and the progression of osteoarthritis in the contralateral hip. [Participants and Methods] This was a retrospective cohort study of 65 patients who underwent primary unilateral total hip arthroplasty for bilateral hip osteoarthritis. The minimum joint space width of the contralateral hip was measured preoperatively. The change in minimum joint space width one year postoperatively compared with preoperatively was measured. At three weeks postoperatively, patients were divided into the perceived and non-perceived leg length discrepancy groups using the block test. Patients with a perceived leg length discrepancy of 2 mm or more and less than 2 mm were grouped into the perceived and non-perceived leg length discrepancy groups, respectively. Before and after propensity score matching, the change in minimum joint space width between the two groups from the preoperative period to one year postoperatively was compared. [Results] In the pre-propensity matching sample, there was no significant difference in the change in minimum joint space width between the two groups. In the post-propensity matching sample, the change in minimum joint space width in the perceived leg length discrepancy group was significantly larger than that in the non-perceived leg length discrepancy group. [Conclusion] The early postoperative perceived leg length discrepancy after unilateral total hip arthroplasty may affect the progression of osteoarthritis in the contralateral hip.

Association between income levels and irregular physician visits after a health checkup, and its consequent effect on glycemic control among employees: A retrospective propensity score-matched cohort study

AIMS/INTRODUCTION

The present study aimed to evaluate the effects of income levels on physician visit patterns and to quantify the consequent impact of irregular physician visits on glycemic control among employees' health insurance beneficiaries in Japan.

MATERIALS AND METHODS

We obtained specific health checkup data of untreated diabetes patients from the Fukuoka branch of the Japanese Health Insurance Association. We selected 2,981 insurance beneficiaries and classified 650 and 2,331 patients into, respectively, the regular visit and irregular visit group. We implemented propensity score matching to select an adequate control group.

RESULTS

Compared with those with a standard monthly income <$2,000 (US$1 = ¥100), those with a higher monthly income were less likely to have irregular visits; $2,000-2,999: odds ratio 0.74 (95% confidence interval 0.56-0.98), $3,000-3,999: odds ratio 0.63 (95% confidence interval 0.46-0.87) and ≥$5,000: odds ratio 0.58 (95% confidence interval 0.39-0.86). After propensity score matching and adjusting for covariates, the irregular visit group tended to have poor glycemic control; increased glycated hemoglobin ≥0.5: odds ratio 1.90 (95% confidence interval 1.30-2.77), ≥1.0: odds ratio 2.75 (95% confidence interval 1.56-4.82) and ≥20% relatively: odds ratio 3.18 (95% confidence interval 1.46-6.92).

CONCLUSIONS

We clarified that there was a significant relationship between income and irregular visits, and this consequently resulted in poor glycemic control. These findings would be useful for more effective disease management.

Risk of hospitalization for diabetic macrovascular complications and in-hospital mortality with irregular physician visits using propensity score matching

AIMS/INTRODUCTION

The objective of the present study was to evaluate the risk of diabetic macrovascular complications and in-hospital mortality among diabetic patients with irregular physician visits.

MATERIALS AND METHODS

We carried out a health insurance-based retrospective cohort study using claims data from diabetic patients who were newly hospitalized between April 2010 and September 2010 among beneficiaries of the Fukuoka National Health Insurance Organization. Regular visits were defined as physician visits for diabetes mellitus at least every 3 months between April 2009 and March 2010, whereas other visits or no visits were defined as irregular visits. We assigned 5,940 patients to the regular visit or the irregular visit groups using propensity score matching. We compared in-hospital mortality and hospitalization for diabetic macrovascular complications between the two groups by multiple logistic regression models.

RESULTS

The irregular visit group had a significantly higher risk of hospitalization for acute myocardial infarction (AMI), ischemic heart diseases (IHDs) except AMI, all IHDs, all strokes and diabetic macrovascular complications than did the regular visit group. Adjusted odds ratios for AMI, IHDs except AMI, all IHDs, all strokes, and diabetic macrovascular complications were 3.52 (95% confidence interval [CI] 1.79-6.96), 1.25 (95% CI 1.02-1.54), 1.37 (95% CI 1.12-1.66), 1.29 (95% CI 1.04-1.60), and 1.28 (95% CI 1.10-1.48), respectively.

CONCLUSIONS

The present study shows that the irregular visit group had significantly higher risks of hospitalization for IHD and stroke among diabetic patients. Insurers need to motivate diabetic beneficiaries to make regular visits to physicians.

Impact of concurrent macrovascular co-morbidities on healthcare utilization in patients with type 2 diabetes in Europe: a matched study

AIM

To examine and to quantify the impact of concurrent macrovascular co-morbidities (MVC) on healthcare resource utilization among patients with type 2 diabetes mellitus (T2DM) in Europe.

METHODS

This is a matched cohort study based on the Real-Life Effectiveness and Care Patterns of Diabetes Management study, a multicentre, observational study with retrospective medical chart reviews of T2DM patients in Spain, France, UK, Norway, Finland, Germany and Poland. Included patients were aged > or =30 years at time of diagnosis of T2DM who added a sulfonylurea or a PPARgamma agonist to failing metformin monotherapy (index date) and had concurrent MVC (cases). A control cohort with T2DM but without concurrent MVC was identified using 1:1 propensity score matching. Logit models were used to identify the relationship between concurrent MVC and the likelihood of emergency room admission, receiving medical/surgical procedures, and hospitalization during the study period after controlling for baseline demographics, clinical information and baseline treatment. Negative binomial models were used to predict the number of office visits and length of hospital stay per year attributable to the concurrent MVC.

RESULTS

Relative to controls, patients with MVC were significantly more likely to have emergency department admissions [odds ratio (OR) 2.69; 95% CI: 1.56-4.65], receiving medical/surgical procedures (OR 2.57; 95% CI: 1.56-4.21) and hospitalizations (OR 2.58; 95% CI: 1.64-4.07) after controlling for other predictors. Similarly, MVC were associated with 1.49 additional office visits per year (p = 0.036) and 0.32 days of hospital stay per year (p = 0.023).

CONCLUSIONS

Within a seven-country European sample, this study showed that T2DM patients with MVC were more likely to use healthcare resources compared with T2DM patients without MVC.

Healthcare costs of atypical antipsychotic use for patients with bipolar disorder in a Medicaid programme

BACKGROUND

A large body of clinical studies have demonstrated the efficacy of atypical antipsychotic use in the treatment of bipolar disorder. Facing increasing budget pressure, third-party payers, such as state Medicaid programmes in the US, are demanding better understanding of the medical costs beyond atypical antipsychotic drug costs alone in treating bipolar disorder.

OBJECTIVE

To examine healthcare costs associated with the atypical antipsychotic treatments for bipolar disorder from a US third-party payer perspective.

METHODS

This was a retrospective cohort study using an intent-to-treat approach. Using the North Carolina Medicaid claims database (August 2000 to January 2005), 3328 patients with bipolar disorder were identified who were continuously eligible for 3 months pre-initiation and 12 months post-initiation of treatment with an atypical antipsychotic (AP2) or mood stabilizer (MS). Patients were classified into three groups based on the treatment types during the first 30 days after treatment initiation: AP2 monotherapy, AP2 + MS combination therapy, and MS monotherapy. Bipolar-related and total health-related costs were examined for the 12-month period. Propensity score matching was employed to balance baseline characteristics among the three comparison groups. Generalized linear models were further employed to estimate the average treatment effect on the cost outcomes.

RESULTS

Compared with MS monotherapy, AP2 monotherapy and AP2 + MS combination therapy incurred higher medication costs during the 12-month treatment period. Patients receiving AP2 monotherapy had significantly lower bipolar-related medical costs (-$US698; p = 0.002) [year 2004 values] than patients receiving MS monotherapy. However, the inclusion of the medication cost produced no statistically significant difference in bipolar-related total cost (p = 0.14). Similar results were observed for all health-related costs. Patients receiving AP2 + MS therapy incurred significantly higher bipolar-related total costs (+$US1659; p < 0.0001) and all health-related total costs (+$US2115; p < 0.0001) than patients receiving MS monotherapy, which was attributable largely to the higher medication cost.

CONCLUSIONS

From a third-party payer perspective, atypical antipsychotic monotherapy generated higher drug costs but lower medical care costs, resulting in equivalent total healthcare costs over a 1-year period.

High-dimensional propensity score adjustment in studies of treatment effects using health care claims data

BACKGROUND

Adjusting for large numbers of covariates ascertained from patients' health care claims data may improve control of confounding, as these variables may collectively be proxies for unobserved factors. Here, we develop and test an algorithm that empirically identifies candidate covariates, prioritizes covariates, and integrates them into a propensity-score-based confounder adjustment model.

METHODS

We developed a multistep algorithm to implement high-dimensional proxy adjustment in claims data. Steps include (1) identifying data dimensions, eg, diagnoses, procedures, and medications; (2) empirically identifying candidate covariates; (3) assessing recurrence of codes; (4) prioritizing covariates; (5) selecting covariates for adjustment; (6) estimating the exposure propensity score; and (7) estimating an outcome model. This algorithm was tested in Medicare claims data, including a study on the effect of Cox-2 inhibitors on reduced gastric toxicity compared with nonselective nonsteroidal anti-inflammatory drugs (NSAIDs).

RESULTS

In a population of 49,653 new users of Cox-2 inhibitors or nonselective NSAIDs, a crude relative risk (RR) for upper GI toxicity (RR = 1.09 [95% confidence interval = 0.91-1.30]) was initially observed. Adjusting for 15 predefined covariates resulted in a possible gastroprotective effect (0.94 [0.78-1.12]). A gastroprotective effect became stronger when adjusting for an additional 500 algorithm-derived covariates (0.88 [0.73-1.06]). Results of a study on the effect of statin on reduced mortality were similar. Using the algorithm adjustment confirmed a null finding between influenza vaccination and hip fracture (1.02 [0.85-1.21]).

CONCLUSIONS

In typical pharmacoepidemiologic studies, the proposed high-dimensional propensity score resulted in improved effect estimates compared with adjustment limited to predefined covariates, when benchmarked against results expected from randomized trials.