Comparing diagnostic coding and laboratory results.

To the Editor: The global Military Health System maintains electronic inpatient (Standard Inpatient Data Record, SIDR) and outpatient (Standard Ambulatory Data Record, SADR) clinical diagnostic coded data generated by the Department of Defense Composite Health Care System (CHCS), an electronic system that tracks and stores administrative and other patient encounter data. Because these records are readily available, widespread monitoring of these data as a means of medical surveillance has been suggested (1,2). Only 1 study in the literature assessed electronic coding reliability of these data (3); those authors found SIDRs to be a reliable source of billing data for common diagnoses, not including notifiable infectious diseases. We compared SADR and SIDR infectious disease diagnostic codes to laboratory data to assess the usefulness of these datasets in notifiable disease surveillance.

We identified SADRs and SIDRs coded for malaria, syphilis, acute hepatitis B, and Lyme disease in sailors, marines, and their family members, who were beneficiaries for medical care in a large metropolitan area. Medical encounters from January 1, 2001, to June 30, 2002, were studied. All records for the same patient with the same diagnostic code(s) were considered as 1 encounter. Records were selected on the basis of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes (4) as defined by the Department of Defense (5). Laboratory data were not part of SIDRs and SADRs but were part of CHCS.

For records with diagnostic codes relating to any of the 4 diseases of interest, laboratory records were searched to determine: 1) whether the provider ordered an appropriate test or tests and 2) if these were ordered, were the test results confirmatory (positive). Appropriate and confirmatory test results were determined by using published references (5-7) and local laboratory practices. For malaria, a blood smear was considered an appropriate test with a positive blood smear accepted as confirmatory (5,6). We considered both nontreponemal and treponemal tests to be appropriate for syphilis but only a positive treponemal test as confirmatory (5,6). For acute hepatitis B, we considered hepatitis B surface antigen or immunoglobulin (Ig) M anti-hepatitis B core (anti-HBc) to be an appropriate test, but only a positive IgM anti-HBc was accepted as confirmatory (5,6). We considered enzyme immunoassay total antibody screens or Western blot (WB) IgG or IgM tests to be appropriate for Lyme disease and accepted any positive test as confirmatory (5-7).) [chi square] calculations were conducted ([alpha] = 0.05).

Twenty-one SIDRs and 155 SADRs met the selection criteria (Table). While 61.9% of SIDRs studied had appropriate laboratory tests ordered, only 19.0% had associated confirmatory results in CHCS. For outpatient records, 64.5% had appropriate tests ordered, and 15.5% had confirmatory results. Among the SADRs, the proportions of appropriate laboratory tests for the diseases studied differed significantly (summary [chi square] =11.5, p = 0.01). These results suggest that tracking electronic SADR and SIDR datasets for the selected reportable diseases could produce a high number of false-positive reports; in this study, 81.0% of inpatient and 84.5% of outpatient reports would lack a confirmatory laboratory test result.

This initial evaluation is limited but supports the need to evaluate electronic datasets before using them for medical surveillance. We examined only ICD-9-CM coded records of selected diseases from 1 geographic area, with resulting small samples. Therefore, our results may not be generalizable. This study was restricted to laboratory, inpatient, and outpatient data recorded within 1 coordinated military system. Laboratory testing or clinical visits may have occurred outside of this network and may not have been captured in this study. Laboratory data were not recorded or stored in a standardized format in CHCS, increasing the likelihood of misclassification. We did not evaluate all related sources of data, including the hard-copy clinical records, so we do not know the completeness of the ICD-9-CM codes or the extent of ICD-9-CM code misclassification. Additionally, local clinical practices in terms of both ordering laboratory tests and coding diagnoses for the diseases studied were not defined.

Future studies would benefit from comparing reported medical events, paper medical records, and electronic datasets to include determination of sensitivity as well as positive predictive value (2,8,9). Discordance in these data sources should be investigated for miscoding, incomplete data, and unexpected clinical practices.

Efforts to improve medical record coding at military medical treatment facilities are under way (10). Additionally, standardization of CHCS laboratory test files, including adoption of the Logical Observation Identifiers Names and Codes system for standardized reporting of test names, is under way (available from http://www.ha.osd.mil/policies/2003/03-023.pdf). However, a documented, complete, reliable, and closely monitored single source of data for medical surveillance and disease reporting does not currently exist. Therefore, surveillance programs for infectious diseases in the US military should include monitoring of multiple, related sources of data and information (e.g., electronic inpatient and outpatient encounters, laboratory results, and pharmacy data). All of these sources should be evaluated for completeness and accuracy.

Table. Clinical records with associated laboratory test results *

                              Inpatient records (SIDR)

                       No.                    No. Confirmatory
                     records     No. tests       results (%)
Disease ([dagger])   selected   ordered (%)   ([double dagger])

Malaria                 3        3 (100.0)        1 (33.3)
Syphilis                1        1 (100.0)        1 (100.0)
Acute hepatitis B       16       8 (50.0)          1 (6.3)
Lyme disease            1        1 (100.0)        1 (100.0)

Total                   21       13 (61.9)        4 (19.0)

                         Outpatient records (SADR)

                       No.
                     records          No. Tests
Disease ([dagger])   selected   ordered (%) (section)

Malaria                 17            8 (47.1)
Syphilis                44            31 (70.4)
Acute hepatitis B       39            32 (82.1)
Lyme disease            55            29 (52.7)

Total                  155           100 (64.5)

                              Outpatient records (SADR)

                                   No. confirmatory
Disease ([dagger])   results (%) ([double dagger]) ([paragraph])

Malaria                                1 (5.9)
Syphilis                              12 (27.3)
Acute hepatitis B                      5 (12.8)
Lyme disease                           6 (10.9)

Total                                 24 (15.5)

* This table presents Standard Inpatient Data Records (SIDR) and
Standard Ambulatory Data Records (SADR) studied and percentages with
appropriate laboratory tests ordered and confirmatory laboratory test
results.

([dagger]) International Classification of Diseases, 9th Revision,
Clinical Modification (ICD-9-CM) codes: malaria, 084.0-084.6; syphilis,
090, 091, 095, 096; acute hepatitis B, 070.30, 070.31; Lyme disease,
088.81.

([double dagger]) Percentages reported reflect the proportion of
records that had positive confirmatory laboratory results.

([section]) Summary [chi square] = 11.5; p = 0.01.

([paragraph]) Summary [chi square] = 7.0; p = 0.07.

Acknowledgments

We thank the Army Medical Surveillance Activity and Tricare Management Activity for data support; and Shilpa Hakre, Danielle Dell, Cara Olsen, and Julie Pavlin for manuscript review.

This study was supported in part by the Department of Defense Global Emerging Infections Surveillance and Response System, Silver Spring, Maryland.

Asha J. Riegodedios, * Anuli Ajene, * Mark A. Malakooti, * Joel C. Gaydos, ([dagger]) Victor H. MacIntosh, ([dagger]) and Bruce K. Bohnker * (1)

* Navy Environmental Health Center, Portsmouth, Virginia, USA; and 1-Department of Defense Global Emerging Infections Surveillance and Response System, Silver Spring, Maryland, USA

(1) Preliminary findings were presented at the US Army Force Health Protection Conference, August 2003, Albuquerque NM, the International Conference on Emerging Infectious Diseases, February 2004, Atlanta, GA, and the Navy Occupational Health and Preventive Medicine Workshop, March 2004, Norfolk, VA.

References

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(2.) Bond MM, Yates SW. Sexually transmitted disease screening and reporting practices in a military medical center. Mil Med. 2000;165:470-2.

(3.) Meyer GS, Krakauer H. Validity of the Department of Defense standard inpatient data record for quality management and health service research. Mil Med. 1998;163:461-5.

(4.) International Classification of Diseases, Ninth Revision, Clinical Modification. Dover (DE): American Medical Association; 1997.

(5.) Office of the Assistant Secretary of Defense. Health Affairs Memo of 18 Nov 1998. Triservice reportable disease document. [accessed 12 Jan 2004]. Available from http://www.tricare.osd.mil/policy/fy98/ TriService_Reportable_Events Document.pdf

(6.) Isada CM, Kasten BL, Goldman MP, Gray LD, Aberg JA. Infectious diseases handbook. 5th ed. Hudson (OH): Lexi-Comp Inc; 2003.

(7.) Cunha BA, editor. Tickborne infectious diseases diagnosis and management. New York: Marcel Dekker, Inc; 2000.

(8.) Campos-Outcalt DE. Accuracy of ICD-9-CM codes in identifying reportable communicable diseases. Quality Assurance and Utilization Review. 1990;5:86-9.

(9.) Yokoe DS, Subramanyan GS, Nardell E, Sharnprapai S, McCray E, Platt R. Supplementing tuberculosis surveillance with automated data from health maintenance organizations. Emerg Infect Dis. 1999;5:779-87.

(10.) Office of the Secretary of Defense- Health Affairs Memorandum of 20 Aug 2003. Improved medical record coding at military healthcare facilities. [accessed 20 Mar 2004]. Available from http://www.pasba. amedd.army.mil/Quality/Resources/MemoI mprovingMRCoding.pdf

Address for correspondence: Asha J. Riegodedios, Navy Environmental Health Center, c/o Naval Dosimetry Center, 8901 Wisconsin Ave, Bethesda, Maryland 20889, USA; fax: [phone]; email: [e-mail]