Validation of Postsurgical Venous Thromboembolism Diagnoses of Patients Undergoing Lower Limb Orthopedic Surgery in the Danish National Patient Registry

Figures & data

Figure 1 Flowchart displaying the selection of study population.

Table 1 Descriptive Statistics of Baseline Characteristics of Included Cases and Comparators Registered in the Danish National Patient Registry During 2009 to 2019 (n = 1172)

	Cases (with VTE Diagnoses) N = 420	Comparators (without VTE Diagnoses) N = 752
Age, years, median (25th-75th percentiles)	68.6 (55.5–78.2)	68.7 (55.9–78.3)
Sex, n (%)
Men	191 (45.5%)	336 (44.7%)
Women	229 (54.5%)	416 (55.3%)
History of VTE before surgery, n (%)
Yes	48 (11.4%)	24 (3.2%)
No	372 (88.6%)	728 (96.8%)
Anatomic site of surgery, n (%)
Pelvis	3 (0.7%)	0 (0%)
Hip joint/femur	201 (47.9%)	357 (47.5%)
Knee/crus	171 (40.7%)	313 (41.6%)
Ankle/foot	45 (10.7%)	82 (10.9%)

Abbreviations: n, total verified diagnoses in medical charts; N, total diagnoses in the Danish National Patient Registry.

Table 2 Positive Predictive Value and Negative Predictive Value of Overall Diagnoses of Venous Thromboembolism Including Deep Venous Thrombosis and Pulmonary Embolism in the Danish National Patient Registry Stratified by Overall, Sex and Surgery Year

Diagnosis	Overall, PPV and NPV				Female, PPV and NPV				Men, PPV and NPV
	n/N	PPV % (95% CI)	n/N	NPV % (95% CI)	n/N	PPV % (95% CI)	n/N	NPV % (95% CI)	n/N	PPV % (95% CI)	n/N	NPV % (95% CI)
VTE	358/420	85.2 (81.5–88.5)	748/752	99.5 (98.6–99.9)	191/229	83.41 (77.9–88.0)	191/229	99.52 (98.3–99.9)	167/191	87.43 (81.9–91.8)	332/334	99.4 (97.9–99.9)
DVT	227/275	82.6 (77.5–86.8)	748/752	99.5 (98.6–99.9)	111/140	79.3 (71.6–85.7)	111/140	99.52 (98.3–99.9)	116/135	85.9 (78.9–91.3)	332/334	99.4 (97.9–99.9)
PE	131/145	90.3 (84.3–94.6)	748/748	100.0 (99.5–100.0)	80/89	89.9 (81.7–95.3)	80/89	100 (99.1–100.0)	51/56	91.1 (80.4–97.0)	332/332	100.0 (98.9–100.0)
Surgery year
	2009–2011				2012–2015				2016–2019
Diagnosis	n/N	PPV % (95% CI)	n/N	NPV % (95% CI)	n/N	PPV % (95% CI)	n/N	NPV % (95% CI)	n/N	PPV % (95% CI)	n/N	NPV % (95% CI)
VTE	85/113	75.2 (66.2–82.9)	203/203	100.0 (98.2–100.0)	114/132	82.6 (75.2–88.5)	299/300	99.7 (98.2–100.0)	159/175	90.9 (85.6–94.7)	310/313	99.1 (97.3–99.8)
DVT	61/84	72.6 (61.8–81.8)	203/203	100.0 (98.2–100.0)	67/79	79.8 (69.6–87.8)	299/300	99.7 (98.2–100.0)	99/112	88.4 (81.0–93.7)	310/313	99.1 (97.3–99.8)
PE	24/29	82.8 (64.2–94.2)	203/203	100.0 (98.2–100.0)	47/53	87.0 (75.1–94.6)	299/299	100.0 (98.8–100.0)	60/63	95.2 (86.7–99.0)	310/310	100.0 (98.8–100.0)

Abbreviations: n, total verified diagnoses in medical charts; N, total diagnoses in the Danish National Patient Registry; PPV, positive predictive value; NPV, negative predictive value; CI, confidence interval; VTE, venous thromboembolism; DVT, deep vein thrombosis; PE, pulmonary embolism.

Table 3 Predictive Values Stratified by Participants Age Groups

Diagnosis	Age Groups
	<40				40–60
	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)
VTE	32/40	80.0 (98.9–100.0)	64/64	100.0 (94.4–100.0)	79/91	86.8 (78.1–93.0)	158/159	99.4 (96.6–100.0)
DVT	26/34	76.5% (58.8–89.3)	64/64	100.0 (94.4–100.0)	59/69	85.5 (75.0–92.8)	158/159	99.4 (96.6–100.0)
PE	6/6	100.0 (54.1–100.0)	64/64	100.0 (94.4–100.0)	20/22	90.9 (70.8–98.9)	158/158	100.0 (97.7–100.0)
	60–80				>80
Diagnosis	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)
VTE	174/205	84.9 (79.2–89.5)	370/372	99.5 (98.1–99.9)	73/84	86.9 (77.8–93.3)	152/153	99.4 (96.4–100.0)
DVT	103/127	81.1 (73.2–87.5)	370/372	99.5 (98.1–99.9)	39/45	86.7 (73.2–95.0)	152/153	99.4 (96.4–100.0)
PE	71/78	91.0 (82.4–96.3)	370/370	100 (99.0–100.0)	34/39	87.2 (72.6–95.7)	152/152	100 (97.6–100.0)

Abbreviations: n, total verified diagnoses in medical charts; N, total diagnoses in the Danish National Patient Registry; PPV, positive predictive value; NPV, negative predictive value; CI, confidence interval; VTE, venous thromboembolism; DVT, deep vein thrombosis; PE, pulmonary embolism.

Table 4 Predictive Values Stratified by Location of Surgery on Limb

Diagnosis	Surgery Site
	Pelvis				Hip/Femur
	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)
VTE	3/3	100.0 (29.2–100.0)	0/0	N/A	176/201	87.6 (82.2–91.8)	355/356	99.7 (98.5–100.0)
DVT	3/3	100.0 (29.2–100.0)	0/0	N/A	102/120	85.0 (77.3–90.9)	355/356	99.7 (98.5–100.0)
PE	0/0	N/A	0/0	N/A	74/81	91.4 (83.0–96.5)	355/355	100.0 (99.0–100.0)
	Knee/Crus				Ankle/Foot
Diagnosis	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)	n/N	PPV% (95% CI)	n/N	NPV% (95% CI)
VTE	139/171	81.3 (74.6–86.8)	307/310	99.0 (97.2–99.8)	40/45	88.9 (76.0–96.3)	82/82	100.0 (95.6–100.0)
DVT	100/126	79.4 (71.3–86.1)	307/310	99.0 (97.2–99.8)	22/26	84.6 (65.1–95.6)	82/82	100.0 (95.6–100.0)
PE	39/45	86.7 (73.2–95.0)	307/307	100.0 (98.8–100.0)	18/19	94.7 (74.0–100.0)	82/82	100.0 (95.6–100.0)

Abbreviations: n, total verified diagnoses in medical charts; N, total diagnoses in the Danish National Patient Registry; PPV, positive predictive value; NPV, negative predictive value; CI, confidence interval; VTE, venous thromboembolism; DVT, deep vein thrombosis; PE, pulmonary embolism.