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

Hyponatremia-associated hospital visits are not reduced by early electrolyte testing in older adults starting antidepressants

BACKGROUND

Clinical practice guidelines recommend early serum electrolyte monitoring when starting antidepressants in older adults due to the increased risk of hyponatremia. It is unclear whether this monitoring improves outcomes.

METHODS

Population-based, retrospective cohort study of Ontario adults aged ≥66 years who initiated therapy with a selective serotonin reuptake inhibitor (SSRI) or selective norepinephrine reuptake inhibitor (SNRI) between April 1, 2013, and January 31, 2020. The index date was the date of the first such prescription, and the exposure of interest was serum electrolyte measurement during the subsequent 7 days. The primary outcome was any emergency department or hospital admission with hyponatremia within 8-60 days of antidepressant initiation. Poisson regression models compared individuals who had versus did not have their serum electrolytes tested in the week following SSRI/SNRI initiation, weighting by propensity score-based overlap weights.

RESULTS

Among the 420,085 patients aged ≥66 years initiating treatment with an SSRI/SNRI, 26,808 (6.4%) had serum electrolytes measured in the subsequent 7 days and 6109 (1.5%) subsequently presented to hospital with hyponatremia. The time from drug initiation to hospitalization varied (median 29, interquartile range [IQR] 17-44 days), and the median sodium concentration measured in the community (136, IQR 133-138 mmol/L) was marginally higher than those at the time of hospitalization (132, IQR 130-134 mmol/L). Patients who underwent electrolyte testing in the week following SSRI/SNRI treatment were more likely to attend an emergency department (ED) or hospital with hyponatremia within 8-60 days relative to those who did not (relative risk = 2.31, 95% confidence interval: 2.16-2.46).

CONCLUSIONS

Testing serum electrolytes in the week after starting an SSRI/SNRI is not associated with a reduced risk of a hospital visit with hyponatremia. These findings do not support current guidelines recommending routine electrolyte monitoring.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Location and outcomes of rehospitalizations after critical illness in a single-payer healthcare system

PURPOSE

Unplanned rehospitalization at a hospital other than the initial hospital may contribute to poor outcomes. We examined the location of rehospitalizations and assessed outcomes following critical illness in a single-payer healthcare system.

MATERIALS AND METHODS

Population-based retrospective cohort study using linked datasets (2012-2017) from Ontario, Canada including adults (≥18 years) with an unplanned rehospitalization within 30-days after an index hospitalization that included an ICU stay with mechanical ventilation. Outcomes were the percentage of 30-day rehospitalizations at non-index hospitals, mortality and costs. We employed logistic regression and generalized linear models to assess associations.

RESULTS

There were 14,997 (16.4%) 30-day rehospitalizations. Of these 2765 (18.4%) occurred in a non-index hospital. Distance of home residence from the index hospital was the strongest predictor of a non-index rehospitalization (adjusted odds ratio (aOR) 8.40, 95%CI 7.05-10.01, highest vs. lowest distance quintile). Within 30-days of rehospitalization, deaths (aOR 0.91, 95%CI (0.80-1.04)) and total healthcare costs (adjusted relative risk 1.03 (1.00-1.06)), were similar for patients readmitted to the index or a non-index hospital.

CONCLUSION

Non-index rehospitalization within 30-days of initial discharge is common following critical illness. These rehospitalizations were not significantly associated with an increased risk of harm or higher costs in a single-payer healthcare system.

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.

Differences in Associations of Antidepressants and Hospitalization Due to Hyponatremia

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) and other antidepressants are important as a cause of hyponatremia. However, most studies have focused on the effect on sodium levels regardless of clinical symptoms, or have been too small to be able to discriminate between the effects of specific antidepressant drugs. The objective of the present study was to investigate the association between different groups of antidepressants and the risk of hospitalization due to hyponatremia.

METHODS

In this register-based case-control study of patients in the general Swedish population, we identified 14,359 individuals with a main diagnosis of hyponatremia. For every case, 4 matched controls were included (n = 57,382). To investigate the temporal aspects of drug-induced hyponatremia, antidepressant exposure was divided into patients with newly initiated and ongoing treatment. Univariable and multivariable logistic regression was used to analyze the association of antidepressant use and hospitalization.

RESULTS

For newly initiated antidepressants, adjusted odds ratios (95% confidence interval) for a main diagnosis of hyponatremia compared with controls were: citalopram 5.50 (4.71-6.44); sertraline 4.96 (3.81-6.48); venlafaxine 5.28 (3.20-8.83); tricyclic antidepressants 1.59 (1.13-2.24); and mirtazapine 2.54 (2.04-3.16). Adjusted odds ratio (confidence interval) for individuals with ongoing treatment ranged from 0.57 (0.52-0.63) for citalopram to 1.08 (0.85-1.36) for other SSRIs.

CONCLUSIONS

There was a strong association between newly initiated treatment with SSRIs or venlafaxine and hospitalization due to hyponatremia. The association for tricyclic antidepressants and mirtazapine was small to moderate. In contrast, there was no evidence that ongoing treatment with antidepressants increases the risk for hospitalization due to 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.

Tramadol for noncancer pain and the risk of hyponatremia

BACKGROUND

Case reports have signaled a possible association between tramadol, a weak opioid analgesic, and hyponatremia. The objective of this study was to determine whether the use of tramadol is associated with an increased risk of hyponatremia, when compared with codeine.

METHODS

Using the UK Clinical Practice Research Datalink and Hospital Episodes Statistics database, a population-based cohort of 332,880 patients initiating tramadol or codeine was assembled from 1998 through 2012. Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) of hospitalization for hyponatremia associated with the use of tramadol, compared with codeine, in the first 30 days after initiation. A similar analysis was conducted within a highly restricted sub-cohort, which additionally excluded patients with any serum sodium level abnormality in the year before cohort entry. All models were adjusted for propensity score quintiles.

RESULTS

The incidence rates of hospitalization for hyponatremia were 4.6 (95% CI, 2.4-8.0) and 1.9 (95% CI, 1.4-2.5) per 10,000 person-months for tramadol and codeine users, respectively. In the adjusted model, the use of tramadol was associated with a 2-fold increased risk of hospitalization for hyponatremia, compared with codeine (adjusted HR 2.05; 95% CI, 1.08-3.86). In the highly restricted sub-cohort, the use of tramadol was associated with an over 3-fold increased risk of hospitalization for hyponatremia, compared with codeine (adjusted HR 3.54; 95% CI, 1.32-9.54).

CONCLUSIONS

In this first population-based study, the use of tramadol was associated with an increased risk of hyponatremia requiring hospitalization.

Hyponatremia and sodium picosulfate bowel preparations in older adults

OBJECTIVES

Bowel preparations are commonly prescribed drugs. Case reports and our clinical experience suggest that sodium picosulfate bowel preparations can precipitate severe hyponatremia in some older adults. At present, this risk is poorly quantified. We investigated the association between sodium picosulfate use and the risk of hyponatremia in older adults.

METHODS

We conducted a population-based retrospective cohort study using six linked administrative databases in Ontario, Canada. All Ontario residents over the age of 65 years who filled an outpatient bowel preparation prescription before colonoscopy were eligible. We enrolled new users of either sodium picosulfate (n=99,237) or polyethylene glycol (n=48,595). The primary outcome was hospitalization with hyponatremia within 30 days of the bowel preparation assessed by database codes. The secondary outcomes were hospitalization with urgent head computed tomography (CT) (a proxy for acute central nervous system disturbance) and all-cause mortality.

RESULTS

The baseline characteristics of the two groups, including patient demographics, comorbid conditions, and concomitant medications, were nearly identical. Compared with polyethylene glycol, sodium picosulfate was associated with a higher risk of hospitalization with hyponatremia (absolute risk increase: 0.05%, 95% confidence interval (CI): 0.04-0.06%, relative risk (RR): 2.4, 95% CI: 1.5-3.9), but not hospitalization with urgent CT head (RR: 1.1, 95% CI: 0.7-1.4) or mortality (RR: 0.9, 95% CI: 0.7-1.3).

CONCLUSIONS

Sodium picosulfate bowel preparations lead to more hyponatremia than polyethylene glycol. There was no evidence of increased risk of acute neurologic symptoms or mortality. The absolute increase in risk of hospitalization with hyponatremia remains low but may be avoidable through appropriate fluid intake or preferential use of polyethylene glycol in some older adults.

Validity of the International Classification of Diseases, 10th revision discharge diagnosis codes for hyponatraemia in the Danish National Registry of Patients

OBJECTIVE

To examine the validity of the International Classification of Diseases, 10th revision (ICD-10) codes for hyponatraemia in the nationwide population-based Danish National Registry of Patients (DNRP) among inpatients of all ages.

DESIGN

Population-based validation study.

SETTING

All somatic hospitals in the North and Central Denmark Regions from 2006 through 2011.

PARTICIPANTS

Patients of all ages admitted to hospital (n=819 701 individual patients) during the study period. The patient could be included in the study more than once, and our study did not restrict to patients with serum sodium measurements (total of n=2 186 642 hospitalisations).

MAIN OUTCOME MEASURE

We validated ICD-10 discharge diagnoses of hyponatraemia recorded in the DNRP, using serum sodium measurements obtained from the laboratory information systems (LABKA) research database as the gold standard. One sodium value <135 mmol/L measured at any time during hospitalisation confirmed the diagnosis. We estimated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for ICD-10 codes for hyponatraemia overall and for cut-off points for increasing hyponatraemia severity.

RESULT

An ICD-10 code for hyponatraemia was recorded in the DNRP in 5850 of the 2 186 642 hospitalisations identified. According to laboratory measurements, however, hyponatraemia was present in 306 418 (14%) hospitalisations. Sensitivity of hyponatraemia diagnoses was 1.8% (95% CI 1.7% to 1.8%). For sodium values <115 mmol/L, sensitivity was 34.3% (95% CI 32.6% to 35.9%). The overall PPV was 92.5% (95% CI 91.8% to 93.1%) and decreased with increasing hyponatraemia severity. Specificity and NPV were high for all cut-off points (≥99.8% and ≥86.2%, respectively). Patients with hyponatraemia without a corresponding ICD-10 discharge diagnosis were younger and had higher Charlson Comorbidity Index scores than patients with hyponatraemia with a hyponatraemia code in the DNRP.

CONCLUSIONS

ICD-10 codes for hyponatraemia in the DNRP have high specificity but very low sensitivity. Laboratory test results, not discharge diagnoses, should be used to ascertain hyponatraemia.

Validity of physician billing claims to identify deceased organ donors in large healthcare databases

Objective

We evaluated the validity of physician billing claims to identify deceased organ donors in large provincial healthcare databases.

Methods

We conducted a population-based retrospective validation study of all deceased donors in Ontario, Canada from 2006 to 2011 (n = 988). We included all registered deaths during the same period (n = 458,074). Our main outcome measures included sensitivity, specificity, positive predictive value, and negative predictive value of various algorithms consisting of physician billing claims to identify deceased organ donors and organ-specific donors compared to a reference standard of medical chart abstraction.

Results

The best performing algorithm consisted of any one of 10 different physician billing claims. This algorithm had a sensitivity of 75.4% (95% CI: 72.6% to 78.0%) and a positive predictive value of 77.4% (95% CI: 74.7% to 80.0%) for the identification of deceased organ donors. As expected, specificity and negative predictive value were near 100%. The number of organ donors identified by the algorithm each year was similar to the expected value, and this included the pre-validation period (1991 to 2005). Algorithms to identify organ–specific donors performed poorly (e.g. sensitivity ranged from 0% for small intestine to 67% for heart; positive predictive values ranged from 0% for small intestine to 37% for heart).

Interpretation

Primary data abstraction to identify deceased organ donors should be used whenever possible, particularly for the detection of organ-specific donations. The limitations of physician billing claims should be considered whenever they are used.

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.

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

OBJECTIVE

To define geographical regions (forward sortation areas; FSAs) in Southwestern Ontario, Canada from which patients would reliably present to a hospital with linked laboratory data if they developed adverse events related to medications dispensed in outpatient pharmacies.

DESIGN

Descriptive research.

SETTING

Forty-five hospitals in Southwestern Ontario, Canada, from 2003 to 2009.

PARTICIPANTS

Patients aged 66 years and older who received an outpatient prescription for any drug and presented to the emergency department in the subsequent 120 days.

MAIN OUTCOME MEASURE

The proportion of patients in a given FSA presenting to an emergency department at a hospital with linked laboratory data versus a hospital without linked laboratory data. To be included in the catchment area at least 90% of emergency department visits in an FSA must have occurred at laboratory-linked hospitals in a given year.

RESULTS

Over the study period, there were 649 713 emergency department visits by patients with recent prescription claims from pharmacies in 1 of 118 FSAs. In total, 141 302 of these patients presented to an emergency department at a laboratory-linked hospital. For the year 2003, 12 FSAs met our criteria to be in the catchment area and this number grew to 25 FSAs by the year 2009.

CONCLUSIONS

The relevant geographical regions for hospitals with linked laboratory data have been successfully identified. Studies can now be conducted using these well-defined areas to obtain reliable information on the incidence and absolute risk of presenting to hospital with laboratory abnormalities in older adults dispensed commonly prescribed medications in outpatient pharmacies.