Improving identification of idiopathic intracranial hypertension patients in Swedish patient register

Nationwide Prevalence and Geographic Variation of Idiopathic Intracranial Hypertension among Women in the United States

PURPOSE

To determine the nationwide prevalence and geographic distribution of idiopathic intracranial hypertension (IIH) among women in the United States.

DESIGN

Retrospective cross-sectional study using Medicaid claims and electronic health record data from the IRIS® Registry (Intelligent Research in Sight) and Sight Outcomes Research Collaborative (SOURCE).

PARTICIPANTS

Female Medicaid beneficiaries 18 to 55 years of age with IIH diagnoses and prescriptions for acetazolamide or methazolamide in 2018 were identified, excluding those with other causes of intracranial hypertension. We calculated the proportion of women with IIH in the United States who were insured by Medicaid by combining analyses from the IRIS Registry and SOURCE.

METHODS

To calculate the number of women with IIH in each state, we divided the number of Medicaid beneficiaries by the proportion of patients insured by Medicaid. We used census data from the 2018 American Community Survey to calculate prevalence.

MAIN OUTCOME MEASURES

We examined geographic variation in IIH prevalence using Moran's I statistic and compared it to obesity prevalence data from the 2018 Behavioral Risk Factor Surveillance System. In a validation study, we compared the calculated prevalence of IIH in Minnesota with similar data from the Rochester Epidemiology Project.

RESULTS

Of 13 959 female Medicaid beneficiaries with IIH, 6828 had a prescription for acetazolamide or methazolamide. In the IRIS Registry and SOURCE, 25% of women with IIH were insured by Medicaid (95% confidence interval [CI], 16%-33%), suggesting that 27 312 women 18 to 55 years of age with IIH were taking acetazolamide or methazolamide in 2018 (6828 / 0.25 = 27 312). Prevalence was 3.44 per 10 000 women (95% CI, 2.61-5.39 per 10 000 women), and significant geographic variation was found (Moran I statistic, 0.20; P = 0.03), with higher prevalence in states where obesity was more common. The calculated prevalence of IIH in Minnesota was statistically equivalent to that identified using Rochester Epidemiology Project data (P < 0.05 for equivalence test).

CONCLUSIONS

Idiopathic intracranial hypertension affects 3.44 per 10 000 women 18 to 55 years of age in the United States with significant geographic variation, some of which is explained by variation in obesity prevalence.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Social Determinants of Health in Idiopathic Intracranial Hypertension

BACKGROUND

Idiopathic intracranial hypertension (IIH) disproportionately affects women from socioeconomically disadvantaged communities, but specific social determinants of health have not been examined.

METHODS

We used data from the National Institutes of Health's All of Us Research Program, an ongoing nationwide study of more than 300,000 diverse individuals in the United States. Height and weight were measured at baseline, and participants completed questionnaires about demographics, health care access, and quality of life. Women aged 18-50 years with IIH were identified through electronic health record data, excluding those with venous thrombosis, meningitis, hydrocephalus, or central nervous system neoplasms. We used logistic regression to compare questionnaire responses for IIH cases and controls, adjusting for age, race, ethnicity, annual income, and body mass index (BMI).

RESULTS

We included 416 women with IIH and 107,111 women without IIH. The mean age was 38 years, and 49.3% identified as non-White. After adjusting for age, race/ethnicity, and BMI, women with IIH were more likely to be unemployed (odds ratio [OR] 1.40, 95% confidential interval [CI]: 1.14-1.71) and report delaying care because of difficulty affording copays (OR 1.47, 95% CI: 1.02-2.10) or specialist care (OR 1.52, 95% CI: 1.06-2.18). They also delayed care because of rural residence (OR 2.08, 95% CI: 1.25-3.47) and transportation limitations (OR 2.23, 95% CI: 1.55-3.20). Although women with IIH were more likely to be non-Hispanic Black (OR 1.66, 95% CI: 1.32-2.09), this association lost significance when controlling for BMI and income (OR 1.27, 95% CI: 0.96-1.68).

CONCLUSIONS

Women with IIH experience adverse social determinants of health beyond those associated with obesity alone.

Establishing a valid cohort of patients with acromegaly by combining the National Patient Register with the Swedish Pituitary Register

PURPOSE

The aim of this study was to establish a valid national cohort of patients diagnosed with acromegaly by combining data from the general National Patient Register (NPR) and the disease-specific Swedish Pituitary Register (SPR).

METHODS

Patients ≥ 18 years of age at diagnosis of acromegaly reported from 1991 to 2018 who were registered in the NPR and/or SPR were included. The diagnosis of acromegaly was considered correct for patients identified in both registers or confirmed through chart review. Medical records were reviewed in two of Sweden´s six health care regions if the patient was reported only in the NPR. An algorithm for the NPR, with criteria requiring multiple diagnosis registrations and tumour and/or surgery codes, was constructed to reduce the number of patients to review in the remaining four regions.

RESULTS

A total of 1866 patients were identified. Among these, 938 were reported in both registers. After application of the algorithm and chart review, the diagnosis was confirmed for 83 of the 906 patients found only in the NPR. Among 22 patients only registered in the SPR, a review of medical records confirmed acromegaly in 13. This resulted in a total of 1034 cases with acromegaly during the study period. The incidence rate of acromegaly in Sweden 1991-2018 was calculated to 4.0/million/year in the entire population and 5.1/million/year among subjects ≥ 18 years of age.

CONCLUSION

The combination of the SPR and NPR established a valid cohort of patients diagnosed with acromegaly and increased the estimated incidence in Sweden.

Predictive Value of International Classification of Diseases Codes for Idiopathic Intracranial Hypertension in a University Health System

BACKGROUND

Misclassification bias is introduced into medical claims-based research because of reliance on diagnostic coding rather than full medical record review. We sought to characterize this bias for idiopathic intracranial hypertension (IIH) and evaluate strategies to reduce it.

METHODS

A retrospective review of medical records was conducted using a clinical data warehouse containing medical records and administrative data from an academic medical center. Patients with 1 or more instances of International Classification of Diseases (ICD)-9 or -10 codes for IIH (348.2 or G93.2) between 1989 and 2017 and original results of neuroimaging (head CT or MRI), lumbar puncture, and optic nerve examination were included in the study. Diagnosis of IIH was classified as definite, probable, possible, or inaccurate based on review of medical records. The positive predictive value (PPV) for IIH ICD codes was calculated for all subjects, subjects with an IIH code after all testing was completed, subjects with high numbers of IIH ICD codes and codes spanning longer periods, subjects with IIH ICD codes associated with expert encounters (ophthalmology, neurology, or neurosurgery), and subjects with acetazolamide treatment.

RESULTS

Of 1,005 patients with ICD codes for IIH, 103 patients had complete testing results and were included in the study. PPV of ICD-9/-10 codes for IIH was 0.63. PPV in restricted samples was 0.82 (code by an ophthalmologist n = 57), 0.70 (acetazolamide treatment n = 87), and 0.72 (code after all testing, n = 78). High numbers of code instances and longer duration between the first and last code instance also increased the PPV.

CONCLUSIONS

An ICD-9 or -10 code for IIH had a PPV of 63% for probable or definite IIH in patients with necessary diagnostic testing performed at a single institution. Coding accuracy was improved in patients with an IIH ICD code assigned by an ophthalmologist. Use of coding algorithms considering treatment providers, number of codes, and treatment is a potential strategy to reduce misclassification bias in medical claims-based research on IIH. However, these are associated with a reduced sample size.

A national Swedish case-control study investigating incidence and factors associated with idiopathic intracranial hypertension

OBJECTIVE

To study the incidence of idiopathic intracranial hypertension in Sweden and to explore whether previously proposed risk factors are associated with idiopathic intracranial hypertension by investigating the odds of exposure one year prior to diagnosis in patients compared to controls.

METHODS

Using Swedish health care registers and validated diagnostic algorithms, idiopathic intracranial hypertension patients diagnosed between 2000-2016 were compared with randomly selected matched controls, five from the general population and five with obesity.

RESULTS

We identified 902 idiopathic intracranial hypertension patients and 4510 matched individuals in each control group. Mean incidence among inhabitants ≥18 years of age was 0.71 per 100,000; rising from 0.53 in 2000-2005 to 0.95 in 2012-2016. There were increased odds for idiopathic intracranial hypertension patients compared to general population for exposure to: kidney failure (odds ratio =13.2 (4.1-42.0)), arterial hypertension (odds ratio =17.5 (10.5-29.3)), systemic lupus erythematosus (odds ratio =13.8 (4.3-44.7)), tetracyclines, sulphonamides, lithium, and corticosteroids. In obese controls, odds ratios were also significantly increased for these exposures. Hormonal contraceptive use and exposure to pregnancy did not appear to be associated factors for idiopathic intracranial hypertension development.

CONCLUSIONS

The incidence of idiopathic intracranial hypertension in Sweden is lower relative to reports from other countries but is on the rise. This case-control study confirms several previously reported risk factors associated with idiopathic intracranial hypertension.

Trends in the Surgical Treatment of Pseudotumor Cerebri Syndrome in the United States

IMPORTANCE

Optic nerve sheath fenestration (ONSF) and cerebrospinal fluid shunting are sometimes used to treat pseudotumor cerebri syndrome (PTCS), but their use patterns are unknown.

OBJECTIVES

To investigate the frequency of surgical PTCS treatment in the United States and to compare patients undergoing ONSF with those treated with shunting.

DESIGN, SETTING, AND PARTICIPANTS

This was a retrospective longitudinal cross-sectional study. Inpatient data were obtained from the National Inpatient Sample (NIS), and outpatient surgical center data were obtained from the National Survey of Ambulatory Surgery (NSAS) and National Hospital Ambulatory Medical Care Survey (NHAMCS). Included in the analysis were 10 720 patients aged 18 to 65 years with a diagnosis code for PTCS, excluding venous thrombosis and other causes of intracranial hypertension. Time trends were explored and logistic regression was used to measure differences according to age, race/ethnicity, sex, Elixhauser comorbidity index, and other patient and hospital characteristics. Data analysis was performed from March 31 to October 7, 2020.

EXPOSURE

Treatment for PTCS, excluding venous thrombosis and other causes of intracranial hypertension.

MAIN OUTCOMES AND MEASURES

Annual number of PTCS-related admissions, ONSFs, and shunt procedures from 2002-2016. Patient and hospital-level characteristics of patients with PTCS undergoing ONSF or shunting were compared.

RESULTS

Between 2010 and 2016, 297 ONSFs were performed and 10 423 shunts were placed as treatment for PTCS. The procedures were most commonly performed in individuals aged 26 to 35 years (39.4%), and 9920 (92.4%) of the surgically treated patients were women. ONSF was more common among younger patients (eg, adjusted odds ratio [AOR] for patients ≥46 years vs those 18-25 years, 0.22; 95% CI, 0.08-0.61) and in Black, Hispanic, or other minority populations (AOR, 2.37; 95% CI, 1.31-4.30) and less common in the South (AOR, 0.34; 95% CI, 0.13-0.88) and West (AOR, 0.15; 95% CI, 0.04-0.58) compared with the Northeast. Total PTCS-related hospitalizations increased from 6081 (95% CI, 5137-7025) in 2002 to 18 020 (95% CI, 16 607-19 433) in 2016. Shunting increased from 2002 to 2011 and subsequently plateaued and declined. ONSF was used much less frequently, and use has not increased. No instances of outpatient ONSF or shunting for PTCS were recorded in the NSAS or NHAMCS databases.

CONCLUSIONS AND RELEVANCE

This study's findings suggest that shunting is more common than ONSF and that the use gap has widened as shunting has increased. However, because overall PTCS-related hospitalizations have increased even more rapidly, the percentage of inpatients with PTCS undergoing surgery has decreased. These trends may reflect changes in medical treatment practices and outcomes or growing limitations in access to ophthalmic surgical expertise.

Validity of International Classification of Diseases Codes for Identifying Neuro-Ophthalmic Disease in Large Data Sets: A Systematic Review

BACKGROUND

Administrative health claims data have been used for research in neuro-ophthalmology, but the validity of International Classification of Diseases (ICD) codes for identifying neuro-ophthalmic conditions is unclear.

EVIDENCE ACQUISITION

We performed a systematic literature review to assess the validity of administrative claims data for identifying patients with neuro-ophthalmic disorders. Two reviewers independently reviewed all eligible full-length articles and used a standardized abstraction form to identify ICD code-based definitions for 9 neuro-ophthalmic conditions and their sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). A quality assessment of eligible studies was also performed.

RESULTS

Eleven articles that met criteria for inclusion are as follows: 3 studies of idiopathic intracranial hypertension (PPV 54%-91% and NPV 74%-85%), 2 studies of giant cell arteritis (sensitivity 30%-96% and PPV 94%), 3 studies of optic neuritis (sensitivity 76%-99%, specificity 83%-100%, PPV 25%-100%, and NPV 98%-100%), 1 study of neuromyelitis optica (sensitivity 60%, specificity 100%, PPV 43%-100%, and NPV 98%-100%), 1 study of ocular motor cranial neuropathies (PPV 98%-99%), and 2 studies of myasthenia gravis (sensitivity 53%-97%, specificity 99%-100%, PPV 5%-90%, and NPV 100%). No studies met eligibility criteria for nonarteritic ischemic optic neuropathy, thyroid eye disease, and blepharospasm. Approximately 45.5% provided only one measure of diagnostic accuracy. Complete information about the validation cohorts, inclusion/exclusion criteria, data collection methods, and expertise of those reviewing charts for diagnostic accuracy was missing in 90.9%, 72.7%, 81.8%, and 36.4% of studies, respectively.

CONCLUSIONS

Few studies have reported the validity of ICD codes for neuro-ophthalmic conditions. The range of diagnostic accuracy for some disorders and study quality varied widely. This should be taken into consideration when interpreting studies of neuro-ophthalmic conditions using administrative claims data.

Infectious and inflammatory disorders might increase the risk of developing idiopathic intracranial hypertension - a national case-control study

Objective

To investigate whether conditions causing inflammatory activation are associated with increased risk of idiopathic intracranial hypertension.

Methods

All newly diagnosed idiopathic intracranial hypertension patients (cases) in Sweden between 2000–2016 were identified using pre-determined algorithms (n = 902) and matched with five controls from the general population and five individuals with an obesity diagnosis (n = 4510) for age, sex, region, and vital status. National health registers provided information on infections, inflammatory disorders and dispensed medications. Conditional logistic regression was used to estimate odds ratios and 95% confidence intervals.

Results

Compared to general population controls, the cases had fourfold increased odds of having an infection (odds ratio = 4.3, 95% confidence interval 3.3–5.6), and threefold increased odds of an inflammatory disorder the year prior to idiopathic intracranial hypertension diagnosis (odds ratio = 3.2, 95% confidence interval 2.4–4.3). Organ specific analyses showed that odds were increased for the study diseases in the respiratory organ, kidney organ and gastrointestinal tract, but not for female genital infections. Similar results were found when comparing idiopathic intracranial hypertension with obese controls though the odds ratios were of lower magnitude. Sub-analyses on exposure to anti-infectious and anti-inflammatory drugs confirmed the increased odds ratios for idiopathic intracranial hypertension patients.

Conclusions

These findings suggest that major inflammatory activation may be a risk factor in idiopathic intracranial hypertension development.