Cited by 234Medical Coding and Health InformationDiabetes Management and ResearchPatient Safety and Medication Errors

Validation of ICD-9-CM coding algorithm for improved identification of hypoglycemia visits

Open access
Ginde, Adit A, Blanc, Phillip G, Lieberman, Rebecca M, Camargo, Carlos A·2008·BMC Endocrine Disorders

Abstract

BACKGROUND: Accurate identification of hypoglycemia cases by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes will help to describe epidemiology, monitor trends, and propose interventions for this important complication in patients with diabetes. Prior hypoglycemia studies utilized incomplete search strategies and may be methodologically flawed. We sought to validate a new ICD-9-CM coding algorithm for accurate identification of hypoglycemia visits. METHODS: This was a multicenter, retrospective cohort study using a structured medical record review at three academic emergency departments from July 1, 2005 to June 30, 2006. We prospectively derived a coding algorithm to identify hypoglycemia visits using ICD-9-CM codes (250.3, 250.8, 251.0, 251.1, 251.2, 270.3, 775.0, 775.6, and 962.3). We confirmed hypoglycemia cases by chart review identified by candidate ICD-9-CM codes during the study period. The case definition for hypoglycemia was documented blood glucose 3.9 mmol/l or emergency physician charted diagnosis of hypoglycemia. We evaluated individual components and calculated the positive predictive value. RESULTS: We reviewed 636 charts identified by the candidate ICD-9-CM codes and confirmed 436 (64%) cases of hypoglycemia by chart review. Diabetes with other specified manifestations (250.8), often excluded in prior hypoglycemia analyses, identified 83% of hypoglycemia visits, and unspecified hypoglycemia (251.2) identified 13% of hypoglycemia visits. The absence of any predetermined co-diagnosis codes improved the positive predictive value of code 250.8 from 62% to 92%, while excluding only 10 (2%) true hypoglycemia visits. Although prior analyses included only the first-listed ICD-9 code, more than one-quarter of identified hypoglycemia visits were outside this primary diagnosis field. Overall, the proposed algorithm had 89% positive predictive value (95% confidence interval, 86-92) for detecting hypoglycemia visits. CONCLUSION: The proposed algorithm improves on prior strategies to identify hypoglycemia visits in administrative data sets and will enhance the ability to study the epidemiology and design interventions for this important complication of diabetes care.

AI snapshot

Written from the paper’s full text.

TL;DR

The study validated a new ICD-9-CM coding algorithm for identifying emergency department hypoglycemia visits, reporting an overall positive predictive value of 89% (95% CI 86–92). The algorithm improved on prior strategies by including code 250.8 and excluding visits with alternate co-diagnoses.

Key findings

  • Among 679 abstracted charts (the abstract reports 636), 436 (64%) were confirmed hypoglycemia cases; inter-rater agreement for chart review was kappa = 0.97.
  • Code 250.8 identified 83% of confirmed hypoglycemia visits; absence of any predetermined co-diagnosis codes improved its PPV from 62% to 92%, while excluding only 10 (2%) true hypoglycemia visits. Code 251.2 identified 13% of confirmed visits.
  • The proposed algorithm had 89% PPV (95% CI 86–92); more than one-quarter of confirmed cases had a candidate code outside the first-listed diagnosis field, and first-position codes had higher PPV than other positions (93% vs. 81%, p < 0.01).
  • Removing code 962.3 increased the algorithm’s PPV from 89% to 91% (95% CI 88–93) while estimated sensitivity remained 97%.

Methods

  • Multicenter, retrospective cohort validation using structured medical record review at three urban academic emergency departments from July 1, 2005 to June 30, 2006; 174,134 ED visits yielded 901 patients and 1,139 candidate visits, with 679 charts abstracted.
  • Candidate ICD-9-CM codes were 250.3, 250.8, 251.0, 251.1, 251.2, 270.3, 775.0, 775.6, and 962.3, searched in all diagnosis fields up to ten; hypoglycemia was confirmed by documented blood glucose 3.9 mmol/l or emergency physician charted diagnosis.
  • Analyses calculated PPV with 95% confidence intervals, kappa for a 10% double-abstracted subgroup, chi-squared tests for site/disposition/code position, and sensitivity analysis assuming missed cases.

Limitations

  • Stated: 25% of charts were missing or incomplete and not abstracted; findings come from three academic EDs and may not generalize; false negatives were not formally evaluated, so only PPV was accurately calculated and sensitivity/specificity/NPV estimates are limited; retrospective chart review may overestimate or underestimate true cases.
  • Evident: the abstract reports 636 reviewed charts while the results report 679 abstracted charts, a discrepancy that complicates interpretation of the validation sample size.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1186/1472-6823-8-4

Cites

29 of 29 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 8 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Chart review confirmed 436 (64%) cases of hypoglycemia among reviewed/abstracted charts.

    “We reviewed 636 charts identified by the candidate ICD-9-CM codes and confirmed 436 (64%) cases of hypoglycemia by chart review.”
    • Also stated in: § Results · plain
      “Based on the chart review, we confirmed 436 (64%) cases of hypoglycemia.”
    Quote in the paperSubstantial claim
  • Findingown data

    More than one-quarter of identified hypoglycemia visits had a candidate ICD-9-CM code outside the first-listed/primary diagnosis field.

    “Although prior analyses included only the first-listed ICD-9 code, more than one-quarter of identified hypoglycemia visits were outside this primary diagnosis field.”
    • Also stated in: § Results · plain
      “Over a quarter of confirmed cases had a candidate code outside of the first-listed diagnosis field.”
    • Also stated in: § Discussion · hedged
      “limitation to the primary diagnosis field would have excluded 27% of hypoglycemia cases.”
    Quote in the paperSubstantial claim
  • Findingown data

    The proposed algorithm had 89% positive predictive value (95% CI 86-92) for detecting hypoglycemia visits.

    “Overall, the proposed algorithm had 89% positive predictive value (95% confidence interval, 86–92) for detecting hypoglycemia visits.”
    • Also stated in: § Results · plain
      “Overall, the proposed algorithm had PPV of 89% (95%CI, 86–92) for detecting hypoglycemia visits.”
    Quote in the paperSubstantial claim
  • Findingown data

    ICD-9-CM code 250.8 identified 83% of confirmed hypoglycemia visits.

    “Diabetes with other specified manifestations (250.8), often excluded in prior hypoglycemia analyses, identified 83% of hypoglycemia visits”
    • Also stated in: § Results · plain
      “The majority (83%) of confirmed cases of hypoglycemia were coded as 250.8.”
    Quote in the paperSubstantial claim
  • Findingown data

    Cases identified by ICD-9-CM code 962.3 had a low PPV of 54%.

    “Post-hoc review of the algorithm performance suggested that cases identified by 962.3 demonstrated low PPV (54%)”
    Quote in the paperSubstantial claim
  • May combine two claims. 10
  • Classified as probably not a substantial claim. 4
  • May combine two claims.

    Findingown data

    Exclusion of alternate co-diagnoses reliably eliminated 85% of false-positive cases coded as 250.8, while eliminating only a small number of true-positive cases.

    “Exclusion of these cases reliably eliminated 85% of false-positive cases coded as 250.8, while eliminating only a small number of true-positive cases.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data

    Removing 962.3 as a candidate code and relying only on 250.8 increased the overall algorithm PPV from 89% to 91% (95% CI 88-93) while estimated sensitivity remained at 97%.

    “When we removed 962.3 as a candidate code and relied only on coding for 250.8 in these cases, the PPV for the overall algorithm increased from 89% to 91% (95%CI, 88–93) while the estimated sensitivity remained at 97%.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data

    There was no significant difference in PPV when data were stratified by study site or ED disposition (p = 0.86 and 0.22, respectively).

    “There was no significant difference in PPV when data were stratified by site or by ED disposition (p = 0.86 and 0.22, respectively).”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationreasoning

    Under the assumption that candidate ICD-9-CM codes captured all ED presentations with hypoglycemia, the algorithm had 97% sensitivity, >99% specificity, and >99% NPV.

    “Based on the assumption that the candidate ICD-9-CM codes captured all ED presentations with hypoglycemia, we estimate that the algorithm had 97% sensitivity, >99% specificity, and >99% NPV.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The candidate ICD-9-CM codes captured all emergency department presentations with hypoglycemia.
  • May combine two claims.

    Interpretationreasoning

    Assuming the algorithm missed at most 10% of hypoglycemia visits, the minimum sensitivity was 88% with NPV and specificity remaining >99%.

    “Assuming the algorithm missed at most 10% of hypoglycemia visits, we estimate a minimum sensitivity of 88% with NPV and specificity remaining >99%.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The algorithm missed at most 10% of hypoglycemia visits.
  • May combine two claims.

    Study design and conductown data

    There were no significant differences in age, sex, race/ethnicity, and distribution of candidate ICD-9-CM codes between abstracted and excluded patients (all p > 0.05).

    “There were no significant differences in age, sex, race/ethnicity, and distribution of candidate ICD-9-CM codes comparing abstracted and excluded patients (all p > 0.05).”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim.

    Premisecitation

    The glucose threshold for hypoglycemia was 3.9 mmol/l, based on the American Diabetes Association Workgroup on Hypoglycemia consensus recommendation.

    “We based the glucose threshold on the consensus recommendation defined by the American Diabetes Association Workgroup on Hypoglycemia [16].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [16] American Diabetes Association Workgroup on Hypoglycemia: Defining and reporting hypoglycemia in diabetes. Diabetes Care. 2005, 28: 1245-1249. 10.2337/diacare.28.5.1245. source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Johnson et al. reported that ICD-9-CM code 250.8 identified over half of hypoglycemia episodes and had a PPV of 73% for their case definition.

    “Johnson, et al. first reported the utility of 250.8 in their strategy to identify ED visits for hypoglycemia [10]. In their analysis, this code also identified over half of hypoglycemia episodes and had a PPV of 73% for their case definition of hypoglycemia.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [10] Johnson ES, Koepsell TD, Reiber G, Stergachis A, Platt R: Increasing incidence of serious hypoglycemia in insulin users. J Clin Epidemiol. 2002, 55: 253-259. 10.1016/S0895-4356(01)00479-6. source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductown data

    The study abstracted 679 charts (75% of visits by unique patients) and excluded 222 patients with missing or incomplete documentation.

    “We abstracted 679 charts (75% of visits by unique patients) and excluded the remaining 222 patients with missing or incomplete documentation.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Premisecitation

    Johnson et al. limited their search to first-listed ICD-9-CM codes and excluded all other diagnosis fields.

    “First, Johnson et al. limited their search to first-listed ICD-9-CM codes and excluded all other diagnosis fields.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [10] Johnson ES, Koepsell TD, Reiber G, Stergachis A, Platt R: Increasing incidence of serious hypoglycemia in insulin users. J Clin Epidemiol. 2002, 55: 253-259. 10.1016/S0895-4356(01)00479-6. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The ICD-9-CM classification system is imperfect for case identification because it was created for reimbursement rather than research purposes.

    “The ICD-9-CM classification system is imperfect for case identification, as it was created for reimbursement rather than research purposes [18].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [18] O'Malley KJ, Cook KF, Price MD, Wildes KR, Hurdle JF, Ashton CM: Measuring diagnoses: ICD code accuracy. HSR. 2005, 40: 1620-1639.

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Retrospective chart review for hypoglycemia may overestimate or underestimate the true number of cases.

    “the accuracy of case confirmation by chart review depended on a retrospective evaluation for hypoglycemia, which may overestimate or underestimate the true number of cases.”
    Quote in the paperNot a substantial claim
12 of 12
  • The authors state this as an assumption.

    The candidate ICD-9-CM codes captured all emergency department presentations with hypoglycemia.

    “Under the ideal assumption that no cases were missed, we calculated estimated point estimates for sensitivity, specificity, and negative predictive values (NPV).”
    “Based on the assumption that the candidate ICD-9-CM codes captured all ED presentations with hypoglycemia, we estimate that the algorithm had 97% sensitivity, >99% specificity, and >99% NPV.”
  • The authors state this as an assumption.

    The algorithm missed at most 10% of hypoglycemia visits.

    “Assuming the algorithm missed at most 10% of hypoglycemia visits, we estimate a minimum sensitivity of 88% with NPV and specificity remaining >99%.”
  • The authors state this as an assumption.

    Chart validation is the gold standard for confirmation of true hypoglycemia visits.

    “We considered this chart validation as the gold standard for confirmation of true hypoglycemia visits.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

  • Abstract case percentage does not match its chart count

    Minor

    The abstract reports 436 confirmed cases among 636 reviewed charts, which is 68.6%, not 64%. The Results section reports 679 reviewed charts, a denominator that does yield approximately 64%.

    Reported 64 · recomputed 68.553459

  • Share of ED visits with possible hypoglycemia is understated

    Minor

    The reported 1,139 visits are approximately 0.65% of 174,134 ED visits, which rounds to 0.7% at one decimal place, not 0.5%.

    Reported 0.5 · recomputed 0.654094

2 of 2

Cites

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Authors
Ginde, A. A., Blanc, P. G., Lieberman, R. M., & Camargo, C. A.
Affiliations
  • Beth Israel Deaconess Medical Center (US)
  • Massachusetts General Hospital (US)
Corresponding author
Ginde, Adit A
Venue
BMC Endocrine Disorders
Published
2008-04-01
Volume
8
Issue
1
Pages
4-4
ISSN
1472-6823 (ISSN-L)
OpenAlex
W2048981123
Cited by
234
References
29
Citations by year
2026: 3 · 2025: 5 · 2024: 7 · 2023: 13 · 2022: 12 · 2021: 21 · 2020: 17 · 2019: 24 · 2018: 28 · 2017: 20 · 2016: 20 · 2015: 18 · 2014: 19 · 2013: 11 · 2012: 3
FWCI
9.55
Type
journal article
Language
en
Open access
Locations
  • BMC Endocrine Disorders (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Topics
  • Health Sciences › Health Professions › Health Information Management › Medical Coding and Health Information
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Management and Research
  • Health Sciences › Health Professions › Emergency Medical Services › Patient Safety and Medication Errors
Keywords
hypoglycemia, diabetes mellitus, emergency department visits, positive predictive value, case definition, blood glucose, chart review validation, diabetes epidemiology, electronic health records

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