Validation of Diagnostic Codes to Identify Glaucoma in Taiwan’s Claims Data: A Multi-Institutional Study

Figures & data

Figure 1 Process of validation study.

Table 1 Accuracy of ICD-9-CM and ICD-10-CM Codes to Identify Glaucoma

	TP, n	FP, n	FN, n	PPV, % (95% CI)	NPV, % (95% CI)	Sensitivity, % (95% CI)	Specificity, % (95% CI)
All glaucoma subtypes	359	31	45	92.1 (88.9–94.5)	90.0 (86.7–92.7)	88.9 (85.4–91.8)	92.6 (90.0–94.9)
ICD-9-CM codes (365.1X, 365.2X, 365.9)	205	18	22	91.9 (87.5–95.2)	90.9 (86.5–94.2)	86.5 (81.5–90.6)	96.5(93.2–98.5)
ICD-10-CM codes (H4010X, H4011X, H4012X, H4020X, H4021X, H4022X, H4023X, H4024X)	154	13	23	92.2 (87.1–95.8)	87.9 (82.4–92.2)	87.0 (81.1–91.6)	92.8 (88.0–96.1)
Primary open-angle glaucoma	170	13	108	92.9 (88.2–96.2)	83.1 (80.0–85.9)	61.2 (55.2–66.9)	97.6 (95.9–98.7)
ICD-9-CM codes (365.1X)	96	7	53	93.2 (86.5–97.2)	85.3 (81.2–88.8)	64.4 (56.2–72.1)	97.8 (95.5–99.2)
ICD-10-CM codes (H4010X, H4011X, H4012X)	74	6	55	92.5 (84.4–97.2)	80.1 (75.0–84.7)	57.4 (48.4–66.0)	97.4 (94.4–99.0)
Primary angle-closure glaucoma	69	6	8	92.0 (83.4–97.0)	98.9 (98.0–99.5)	89.6 (80.6–95.4)	99.2 (98.3–99.7)
ICD-9-CM codes (365.2X)	52	4	2	92.9 (82.7–98.0)	99.5 (98.2–99.9)	96.3 (87.3–99.6)	99.0 (97.5–99.7)
ICD-10-CM codes (H4020X, H4021X, H4022X, H4023X, H4024X)	17	2	6	89.5 (75.7–98.7)	98.2 (96.2–99.4)	73.9 (51.6–89.8)	99.4 (97.9–99.9)
Unspecified glaucoma*	120	27	N/A	81.6 (74.4–87.5)	N/A	N/A	N/A
ICD-9-CM code (365.9)	69	15	N/A	82.1 (72.3–89.7)	N/A	N/A	N/A
ICD-10-CM code (H409)	51	12	N/A	81.0 (69.1–89.8)	N/A	N/A	N/A

Notes: *We only calculated the PPVs of ICD-9-CM and ICD-10-CM unspecified glaucoma codes, because no false negative cases could be detected with these codes.

Abbreviations: TP, True positive; FP, false positive; FN, false negative; ICD-9-CM code, International Classification of Diseases Code; 9th Revision; Clinical Modification; ICD-10-CM, International Classification of Diseases; 10th Revision; Clinical Modification; PPV, positive predictive value; NPV, negative predictive value; CI, confidence interval; N/A, not applicable.

Table 2 Reasons for False-Positive Glaucoma Cases

Reasons	n (%)
All glaucoma subtypes (n=31)
Tentative diagnosis to rule out glaucoma but final interpretation was normal visual field	18 (58.1)
Borderline glaucomatous finding without significant visual field progression during serial follow-ups	8 (25.8)
Misclassification
Retinitis pigmentosa	2 (6.5)
Optic neuritis	1 (3.2)
Age-related macular degeneration	1 (3.2)
Pituitary tumor	1 (3.2)
Primary open angle glaucoma (n=13)
Tentative diagnosis to rule out glaucoma but final interpretation was normal visual field	1 (7.7)
Misclassification
Primary angle closure glaucoma	8 (61.5)
Secondary glaucoma	4 (30.8)
Primary angle closure glaucoma (n=6)
Tentative diagnosis to rule out glaucoma but final interpretation was normal visual field	2 (33.3)
Misclassification
Secondary glaucoma	3 (50.0)
Age-related macular degeneration	1 (16.7)
Unspecified glaucoma (n=27)
Tentative diagnosis to rule out glaucoma but final interpretation was normal visual field	15 (55.6)
Borderline glaucomatous finding without significant visual field progression during serial follow-ups	8 (29.6)
Misclassification
Retinitis pigmentosa	2 (7.4)
Optic neuritis	1 (3.7)
Pituitary tumor	1 (3.7)

Notes: *Concurrent coding for both primary open-angle glaucoma and unspecified glaucoma was carried out in 15 false-positive glaucoma cases.