Detection of Cases

Table 23.13 summarizes the results of studies of case detection using only ICD-coded data. The hypothesis underlying these studies is Hypothesis 1: An individual ICD code or a code set can discriminate between whether a patient has syndrome or disease X or not. We have grouped the studies in Table 23.13 by syndrome. Each row reports the sensitivity and specificity of an ICD code or code set for a particular syndrome or diagnosis. For convenient reference, we also computed the likelihood ratio positive and negative.

Unlike chief complaints, in which the syndromes studied are at coarse level of diagnostic precision (e.g., respiratory), research on ICD code sets has also studied code sets that are diagnostically precise. For this reason, we have grouped the published studies into those using diagnostically less precise and diagnostically more precise code sets.

Detection of Less Diagnostically Precise Syndromes. Four studies measured the case detection accuracy of less diagnostically precise ICD code sets. Only one study measured the case detection accuracy of a DoD-GEIS or CDC/DoD code set.

Espino and Wagner conducted the first study of case detection accuracy of an ICD code set for a diagnostically imprecise syndrome (Espino and Wagner, 2001).They studied the ability of ICD codes for ED chief complaints and ICD codes for ED diagnoses to detect patients with acute respiratory syndrome (defined as symptom duration of five days or less). In this ED, registration clerks assigned ICD codes to the chief complaints and ED physicians assigned ICD codes to the diagnoses at the time of the patient's visit. Two internists created the gold standard by reviewing the dictated ED visit note and assigning patients to acute respiratory if the duration of illness was five days or less and the patient had respiratory symptoms, abnormal pulmonary examination, or radiological evidence of pneumonia. The sensitivity and specificity of a respiratory ICD code set (that contained 64 ICD codes) for detecting patients with acute respiratory illness from chief complaints were 0.44 and 0.97, respectively. The sensitivity and specificity of the same respiratory code set for detecting patients with acute respiratory illness from diagnoses were 0.43 and 0.97, respectively. The accuracy of ED diagnoses was not significantly different from the accuracy of ED chief complaints.

Betancourt (2003) studied the case detection accuracy of three DoD-GEIS ICD code sets. He used manual review of medical records by two primary care physicians as the gold standard. He found that the sensitivity of the respiratory, fever, and gastrointestinal code sets was 0.65, 0.71, and 0.90, respectively. All three code sets had a specificity of 0.94.

Ivanov et al. (2002) studied the case detection accuracy of ICD codes for the detection of acute gastrointestinal illness (duration of illness two weeks or less) in EDs. ED physicians assigned ICD codes for diagnoses after seeing a patient. Review of the transcribed emergency-department report by two internists was the gold standard. As in the study by Espino and Wagner, the internists were instructed to label a patient as acute gastrointestinal if symptoms were of duration two weeks or less.They found that an ICD code set (that contained 16 ICD codes) had a sensitivity and specificity of 0.32 and 0.99, respectively, for the detection of acute gastrointestinal syndrome.

Beitel et al. (2004) studied the case detection accuracy of ICD codes for the detection of respiratory, lower respiratory, and upper respiratory syndromes in a pediatric ED. They do not state whether physicians or billing administrators assigned the ICD codes that they studied (but mention that both groups assign ICD codes to ED visits). They used single-physician review of the medical record as the gold standard. The sensitivity and specificity of their respiratory ICD code set was 0.70 and 0.98, respectively, for detection of respiratory syndrome. Similarly, the sensitivity and specificity of their upper respiratory ICD code set was 0.56 and 0.98 for upper table 23.13 Performance of ICD Codes and Code Sets in Detecting Syndromes and Diseases

ICD Code or Code Set Being Tested

Reference Standard for Comparison

Sensitivity

Specificity

Positive

Likelihood Ratio

Negative Likelihood Ratio

Respiratory Syndrome Respiratory code set, ICD codes for ED chief complaints" Respiratory code set, ICD codes for ED diagnosesa Respiratory code set4

Respiratory code set"

Combined chief complaint and respiratory code set"

Lower respiratory syndrome Lower respiratory code set" Upper respiratory syndrome Lower respiratory code set"

Gastrointestinal syndrome Gastrointestinal code setd

Gastrointestinal code set4

Fever

Fever code set4

Pneumococcal pneumonia 038.00 Streptococcal septicemia" 038.20 Pneumococcal septicemiae 481 Pneumococcal pneumonia (or lobar pneumonia, organism unspecified)e 482.30 Pneumonia due to

Streptococcus'1 486 Pneumonia, organism unspecifiede 518.81 Respiratory failuree Pneumococcal pneumonia code set (038.00, 038.20,481, 482.30, 486, 518.81)e Pneumococcal pneumonia code set (038.00, 038.20,481, 482.30)e

Tuberculosis

Tuberculosis code set (all ICD

codes with tuberculosis in title)'' HIV

HIV/AIDS code set (042, 043,

044,795.8)8 AIDS

HIV/AIDS code set (042, 043, 044,795.8)8

Two internist-review of dictated ED note Two internist-review of dictated ED note Two physician-review of medical record Single physician review of medical record Single physician review of medical record

Single physician review of medical record

Single physician review of medical record

Two internist-review of dictated ED note Two physician-review of medical record

Two physician-review of medical record

Microbiology cultures Microbiology cultures Microbiology cultures

Microbiology cultures

Microbiology cultures

Microbiology cultures Microbiology cultures

Microbiology cultures

Review of medical record Review of medical record

Review of medical record

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