Identifying geographical regions serviced by hospitals to assess laboratory-based outcomes

Identifying Ontario geographic regions to assess adults who present to hospital with laboratory-defined conditions: a descriptive study

BACKGROUND

In 2007, an electronic repository called the Ontario Laboratories Information System (OLIS) was introduced to allow health care providers timely access to laboratory test results. Since not all laboratories began submitting their data to OLIS simultaneously, we sought to create a date-dependent table of geographic regions (forward sortation areas [FSAs]) from which people would likely present to a hospital linked to OLIS.

METHODS

In this descriptive study, we used administrative data to capture adults in Ontario who presented to the emergency department for any reason from 2007 to 2017. To assess changes over time, we classified all emergency department visits into fiscal quarters. The primary outcome measure was the proportion of people in a given FSA presenting to an emergency department at an OLIS-linked hospital (v. a hospital not linked to OLIS). To be included in the catchment area, at least 90% of all emergency department visits in a given quarter from a given FSA must have occurred at an OLIS-linked hospital.

RESULTS

By Dec. 31, 2017, 323 (61.4%) of 526 Ontario FSAs were in the catchment area (a population of about 8.5 million). There were no differences in selected demographic characteristics or comorbidities between people residing within the catchment area of OLIS-linked hospitals and those residing in the catchment area of unlinked hospitals on Dec. 31, 2017. We used the FSA information to construct a date-dependent table of geographic areas likely to have hospital laboratory data available in OLIS for future studies.

INTERPRETATION

We identified relevant Ontario geographic regions from which people would likely present to a hospital linked to OLIS. These geographic regions constitute a catchment area that may be used in future studies to capture adults who present to an OLIS-linked hospital with laboratory-defined conditions such as acute kidney injury, hyperkalemia and hyponatremia.

Second-Generation Antidepressants and Hyponatremia Risk: A Population-Based Cohort Study of Older Adults

BACKGROUND

Hyponatremia may occur after initiation of a second-generation antidepressant drug. However, the magnitude of this risk among older adults in routine care is not well characterized.

STUDY DESIGN

Retrospective, population-based, matched-cohort study.

SETTING & PARTICIPANTS

In Ontario, Canada, 2003 to 2012, we compared older adults with a mood or anxiety disorder who were dispensed 1 of 9 second-generation antidepressant drugs with matched adults with comparable indicators of baseline health who were not dispensed an antidepressant drug (n=138,246 per group). A similar comparison was made in a subpopulation with available laboratory data (n=4,186 per group).

PREDICTOR

Second-generation antidepressant prescription versus no antidepressant prescription.

OUTCOMES

The primary outcome was hospitalization with hyponatremia. A secondary outcome was hospitalization with both hyponatremia and delirium.

MEASUREMENTS

We assessed hospitalization with hyponatremia using a diagnosis code and, in the subpopulation, serum sodium values. We assessed hospitalization with hyponatremia and delirium using a combination of diagnosis codes.

RESULTS

Second-generation antidepressant use versus nonuse was associated with higher 30-day risk for hospitalization with hyponatremia (450/138,246 [0.33%] vs 84/138,246 [0.06%]; relative risk [RR], 5.46 [95% CI, 4.32-6.91]). This association was consistent in the subpopulation with serum sodium values (73/4,186 [1.74%] vs 18/4,186 [0.43%]; RR, 4.23 [95% CI, 2.50-7.19]; absolute risk increase, 1.31% [95% CI, 0.87%-1.75%]). Second-generation antidepressant use versus nonuse was also associated with higher 30-day risk for hospitalization with both hyponatremia and delirium (28/138,246 [0.02%] vs 7/138,246 [0.005%]; RR, 4.00 [95% CI, 1.75-9.16]).

LIMITATIONS

Measures of serum sodium could be ascertained in only a subpopulation.

CONCLUSIONS

Use of a second-generation antidepressant in routine care by older adults is associated with an approximate 5-fold increase in 30-day risk for hospitalization with hyponatremia compared to nonuse. However, the absolute increase in 30-day incidence is low.

Atypical antipsychotic medications and hyponatremia in older adults: a population-based cohort study

BACKGROUND

A number of case reports have suggested a possible association between atypical antipsychotic medications and hyponatremia. Currently, there are no reliable estimates of hyponatremia risk from atypical antipsychotic drugs.

OBJECTIVE

The objective of this study was to examine the 30-day risk of hospitalization with hyponatremia in older adults dispensed an atypical antipsychotic drug relative to no antipsychotic use.

DESIGN

The design of this study was a retrospective, population-based cohort study.

SETTING

The setting of this study was in Ontario, Canada, from 2003 to 2012.

PATIENTS

Adults 65 years or older with an identified psychiatric condition who were newly dispensed risperidone, olanzapine, or quetiapine in the community setting compared to adults with similar indicators of baseline health who were not dispensed such a prescription.

MEASUREMENTS

The primary outcome was the 30-day risk of hospitalization with hyponatremia. The tracer outcome (an outcome that is not expected to be influenced by the study drugs) was the 30-day risk of hospitalization with bowel obstruction. These outcomes were assessed using hospital diagnosis codes.

METHODS

Using health administrative data, we applied a propensity score technique to match antipsychotic users 1:1 to non-users of antipsychotic drugs (58,008 patients in each group). We used conditional logistic regression to compare outcomes among the matched users and non-users.

RESULTS

A total of 104 baseline characteristics were well-balanced between the two matched groups. Atypical antipsychotic use compared to non-use was associated with an increased risk of hospitalization with hyponatremia within 30 days (86/58,008 (0.15 %) versus 53/58,008 (0.09 %); relative risk 1.62 (95 % confidence interval (CI) 1.15 to 2.29); absolute risk increase 0.06 % (95 % CI 0.02 to 0.10)). The limited number of events precluded some additional analyses to confirm if the association was robust. Atypical antipsychotic use compared to non-use was not associated with hospitalization with bowel obstruction within 30 days (55/58,008 (0.09 %) versus 44/58,008 (0.08 %); relative risk 1.25 (95 % CI 0.84 to 1.86)).

LIMITATIONS

We could only study older adults within our data sources.

CONCLUSIONS

In this study, the use of an atypical antipsychotic was associated with a modest but statistically significant increase in the 30-day risk of a hospitalization with hyponatremia. The association was less pronounced than that described with other psychotropic drugs.

The risk of pancreatitis with sitagliptin therapy in older adults: a population-based cohort study

BACKGROUND

The risk of pancreatitis with sitagliptin use in routine care remains to be established in older patients. We aimed to determine this risk in older adults who were newly prescribed sitagliptin versus an alternative hypoglycemic agent in the outpatient setting.

METHODS

In a population-based retrospective cohort study in Ontario from 2010 until 2012 involving adults aged 66 years and older, we studied those who were newly prescribed sitagliptin or an alternative hypoglycemic agent. Our primary outcome of interest was a hospital encounter (emergency department visit or hospital admission) with acute pancreatitis within 90 days. We used inverse probability of treatment weighting to balance the 2 groups and logistic regression with a robust variance estimate to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

A total of 57 689 patients (mean age 74 yr) were newly prescribed sitagliptin, and 83 405 patients (mean age 75 yr) were given an alternative hypoglycemic agent (metformin, glyburide, gliclazide or insulin) during the study period. After weighting, there were no significant differences in measured baseline characteristics between groups. In the weighted sample, sitagliptin was not associated with an increased risk of a hospital encounter with pancreatitis compared with alternative hypoglycemic agents (weighted total 46 of 57 689 patients taking sitagliptin [0.08%] v. 48 of 55 705 patients taking alternative hypoglycemic agents [0.09%], absolute risk difference -0.01% [95% CI -0.05% to 0.02%], OR 0.92 [95% CI 0.55 to 1.55]).

INTERPRETATION

Older adults newly prescribed sitagliptin in routine care were not at a substantially higher risk of pancreatitis than those prescribed alternative hypoglycemic agents. These findings are reassuring for those who use or prescribe sitagliptin in the management of type 2 diabetes.

Higher anti-depressant dose and major adverse outcomes in moderate chronic kidney disease: a retrospective population-based study

BACKGROUND

Many older patients have chronic kidney disease (CKD), and a lower dose of anti-depressants paroxetine, mirtazapine and venlafaxine is recommended in patients with CKD to prevent drug accumulation from reduced elimination. Using information available in large population-based healthcare administrative databases, we conducted this study to determine if ignoring the recommendation and prescribing a higher versus lower dose of anti-depressants associates with a higher risk of adverse events.

METHODS

We conducted a population-based cohort study to describe the 30-day risk of delirium in older adults who initiated a higher vs. lower dose of these three anti-depressants in routine care. We defined delirium using the best proxy available in our data sources - hospitalization with an urgent head computed tomography (CT) scan. We determined if CKD status modified the association between anti-depressant dose and outcome, and examined the secondary outcome of 30 day all-cause mortality. We used multivariable logistic regression analyses to estimate adjusted odds ratios (relative risk (RR)) and 95% confidence intervals.

RESULTS

We identified adults (mean age 75) in Ontario who started a new study anti-depressant at a higher dose (n=36,651; 31%) or lower dose (n=81,160; 69%). Initiating a higher vs. lower dose was not associated with an increased risk of hospitalization with head CT (1.09% vs. 1.27% (adjusted RR 0.90; 95% CI, 0.80 to 1.02), but was associated with a lower risk of all-cause mortality (0.76% vs. 0.97% RR 0.82; 95% CI, 0.71 to 0.95). Neither of these relative risks were modified by the presence of CKD (p=0.16, 0.68, respectively).

CONCLUSIONS

We did not observe an increase in two adverse outcomes when study anti-depressants were initiated at a higher dose in elderly patients with moderate CKD. Contrary to our hypothesis, the 30-day risk of mortality was lower when a higher versus lower dose of anti-depressant was initiated in these patients, a finding which requires corroboration and further study.

Determinants of wait time for infant inguinal hernia repair in a Canadian children's hospital

BACKGROUND

Longer wait time for infant inguinal hernia (IH) repair is associated with higher complication rates. We wished to determine if socioeconomic and demographic factors influence wait times for IH repair.

METHODS

Children <2 years old with IH at a Canadian children's hospital were retrospectively reviewed. Days from diagnosis to surgical consultation (W1) and from consultation to repair (W2) were collected along with demographic, medical, and socioeconomic data. Linear regression analysis was performed.

RESULTS

A total of 131 patients were appropriate for analysis (82.4% male). Median distance to hospital was 27.5 km (IQR=10.5-50.4) and median income was $34,477 (IQR=30,127-41,986). Median W1, W2, and Wtotal (W1+W2) were 24 (IQR=8-48), 43 (IQR=21-69) and 79 (IQR=38-112) days, respectively. Wait times were shorter in infants who were male (p=0.044), symptomatic (p<0.001), diagnosed in the ED (p<0.001), or had an incarcerated hernia (p=0.006). They were longer for premature infants (p=0.009) and those with significant comorbidities (p=0.018). Neither income (p=0.328) nor distance from hospital (p=0.292) was associated with longer wait times.

CONCLUSION

Wait times for IH repair were appropriately influenced by medical risk factors. Income and distance to hospital did not appear to influence wait times. A population-based study is needed to determine if these findings reflect a general trend within the Canadian health care system.

Detecting chronic kidney disease in population-based administrative databases using an algorithm of hospital encounter and physician claim codes

Background

Large, population-based administrative healthcare databases can be used to identify patients with chronic kidney disease (CKD) when serum creatinine laboratory results are unavailable. We examined the validity of algorithms that used combined hospital encounter and physician claims database codes for the detection of CKD in Ontario, Canada.

Methods

We accrued 123,499 patients over the age of 65 from 2007 to 2010. All patients had a baseline serum creatinine value to estimate glomerular filtration rate (eGFR). We developed an algorithm of physician claims and hospital encounter codes to search administrative databases for the presence of CKD. We determined the sensitivity, specificity, positive and negative predictive values of this algorithm to detect our primary threshold of CKD, an eGFR <45 mL/min per 1.73 m² (15.4% of patients). We also assessed serum creatinine and eGFR values in patients with and without CKD codes (algorithm positive and negative, respectively).

Results

Our algorithm required evidence of at least one of eleven CKD codes and 7.7% of patients were algorithm positive. The sensitivity was 32.7% [95% confidence interval: (95% CI): 32.0 to 33.3%]. Sensitivity was lower in women compared to men (25.7 vs. 43.7%; p <0.001) and in the oldest age category (over 80 vs. 66 to 80; 28.4 vs. 37.6 %; p < 0.001). All specificities were over 94%. The positive and negative predictive values were 65.4% (95% CI: 64.4 to 66.3%) and 88.8% (95% CI: 88.6 to 89.0%), respectively. In algorithm positive patients, the median [interquartile range (IQR)] baseline serum creatinine value was 135 μmol/L (106 to 179 μmol/L) compared to 82 μmol/L (69 to 98 μmol/L) for algorithm negative patients. Corresponding eGFR values were 38 mL/min per 1.73 m² (26 to 51 mL/min per 1.73 m²) vs. 69 mL/min per 1.73 m² (56 to 82 mL/min per 1.73 m²), respectively.

Conclusions

Patients with CKD as identified by our database algorithm had distinctly higher baseline serum creatinine values and lower eGFR values than those without such codes. However, because of limited sensitivity, the prevalence of CKD was underestimated.

Validity of the International Classification of Diseases 10th revision code for hyperkalaemia in elderly patients at presentation to an emergency department and at hospital admission

OBJECTIVES

Evaluate the validity of the International Classification of Diseases, 10th revision (ICD-10) code for hyperkalaemia (E87.5) in two settings: at presentation to an emergency department and at hospital admission.

DESIGN

Population-based validation study.

SETTING

12 hospitals in Southwestern Ontario, Canada, from 2003 to 2010.

PARTICIPANTS

Elderly patients with serum potassium values at presentation to an emergency department (n=64 579) and at hospital admission (n=64 497).

PRIMARY OUTCOME

Sensitivity, specificity, positive-predictive value and negative-predictive value. Serum potassium values in patients with and without a hyperkalaemia code (code positive and code negative, respectively).

RESULTS

The sensitivity of the best-performing ICD-10 coding algorithm for hyperkalaemia (defined by serum potassium >5.5 mmol/l) was 14.1% (95% CI 12.5% to 15.9%) at presentation to an emergency department and 14.6% (95% CI 13.3% to 16.1%) at hospital admission. Both specificities were greater than 99%. In the two settings, the positive-predictive values were 83.2% (95% CI 78.4% to 87.1%) and 62.0% (95% CI 57.9% to 66.0%), while the negative-predictive values were 97.8% (95% CI 97.6% to 97.9%) and 96.9% (95% CI 96.8% to 97.1%). In patients who were code positive for hyperkalaemia, median (IQR) serum potassium values were 6.1 (5.7 to 6.8) mmol/l at presentation to an emergency department and 6.0 (5.1 to 6.7) mmol/l at hospital admission. For code-negative patients median (IQR) serum potassium values were 4.0 (3.7 to 4.4) mmol/l and 4.1 (3.8 to 4.5) mmol/l in each of the two settings, respectively.

CONCLUSIONS

Patients with hospital encounters who were ICD-10 E87.5 hyperkalaemia code positive and negative had distinct higher and lower serum potassium values, respectively. However, due to very low sensitivity, the incidence of hyperkalaemia is underestimated.

Validity of the International Classification of Diseases 10th revision code for hospitalisation with hyponatraemia in elderly patients

OBJECTIVE

To evaluate the validity of the International Classification of Diseases, 10th Revision (ICD-10) diagnosis code for hyponatraemia (E87.1) in two settings: at presentation to the emergency department and at hospital admission.

DESIGN

Population-based retrospective validation study.

SETTING

Twelve hospitals in Southwestern Ontario, Canada, from 2003 to 2010.

PARTICIPANTS

Patients aged 66 years and older with serum sodium laboratory measurements at presentation to the emergency department (n=64 581) and at hospital admission (n=64 499).

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive predictive value and negative predictive value comparing various ICD-10 diagnostic coding algorithms for hyponatraemia to serum sodium laboratory measurements (reference standard). Median serum sodium values comparing patients who were code positive and code negative for hyponatraemia.

RESULTS

The sensitivity of hyponatraemia (defined by a serum sodium ≤132 mmol/l) for the best-performing ICD-10 coding algorithm was 7.5% at presentation to the emergency department (95% CI 7.0% to 8.2%) and 10.6% at hospital admission (95% CI 9.9% to 11.2%). Both specificities were greater than 99%. In the two settings, the positive predictive values were 96.4% (95% CI 94.6% to 97.6%) and 82.3% (95% CI 80.0% to 84.4%), while the negative predictive values were 89.2% (95% CI 89.0% to 89.5%) and 87.1% (95% CI 86.8% to 87.4%). In patients who were code positive for hyponatraemia, the median (IQR) serum sodium measurements were 123 (119-126) mmol/l and 125 (120-130) mmol/l in the two settings. In code negative patients, the measurements were 138 (136-140) mmol/l and 137 (135-139) mmol/l.

CONCLUSIONS

The ICD-10 diagnostic code for hyponatraemia differentiates between two groups of patients with distinct serum sodium measurements at both presentation to the emergency department and at hospital admission. However, these codes underestimate the true incidence of hyponatraemia due to low sensitivity.