The levels of WBC, CRP, ESR, plasma fibrinogen, plasma D-dimer, PC, PCT, and PC/MPV were significantly higher in group infected nonunion than in group aseptic nonunion (P < 0.05). On the contrary, the levels of MPV and PDW were significantly lower in group infected nonunion than in group aseptic nonunion (P < 0.05). The laboratory ranges for the tested markers are shown in Table 2.
Table 2
Comparison of the tested markers in the two groups
| Group A (n = 96) | Group B (n = 201) | P-value |
WBC (109/µL) | | | |
Median | 7.0 | 6.1 | < 0.001* |
P25, P75 | 5.8 ~ 8.6 | 5.3 ~ 7.4 | |
PC (10^9/L) | | | < 0.001* |
Median | 303.0 | 209.0 | |
P25, P75 | 221.8 ~ 404.0 | 178.5 ~ 259.5 | |
PCT (%) | | | < 0.001* |
Median | 0.32 | 0.23 | |
P25, P75 | 0.25 ~ 0.38 | 0.19 ~ 0.27 | |
PDW(%) | | | < 0.001* |
Median | 15.8 | 16.0 | |
P25, P75 | 15.4 ~ 16.2 | 15.5 ~ 16.4 | |
MPV(fl) | | | 0.008* |
Median | 9.1 | 10.1 | |
P25, P75 | 8.2 ~ 10.2 | 9.4 ~ 11.6 | |
PC/MPV | | | < 0.001* |
Median | 34.5 | 20.2 | |
P25, P75 | 22.5 ~ 45.1 | 16.1 ~ 26.6 | |
CRP (mg/L) | | | < 0.001* |
Median | 8.6 | 3.7 | |
P25, P75 | 4.9 ~ 29.7 | 2.5 ~ 5.4 | |
ESR (mm/hr) | | | < 0.001* |
Median | 26.5 | 8.0 | |
P25, P75 | 16.0 ~ 52.5 | 5.0 ~ 14.0 | |
Plasma D-dimer (mg/L) | | | < 0.001* |
Median | 1.10 | 0.36 | |
P25, P75 | 0.49 ~ 2.85 | 0.20 ~ 0.75 | |
Plasma fibrinogen (mg/L) | | | < 0.001* |
Median | 3.8 | 2.6 | |
P25, P75 | 2.9 ~ 5.3 | 2.3 ~ 3.1 | |
Group A = infected nonunion; Group B = aseptic nonunion. |
All P-values calculated using Mann-Whitney U test. |
*P < 0.05 indicates statistical significance. |
WBC, white blood cell; PC, platelet count; PCT, plateletcrit; MPV, mean platelet volume; PDW, platelet distribution width CRP; C-reactive protein; ESR, erythrocyte sedimentation rate. |
All tested markers were evaluated and depicted in one receiver operating characteristic curve (Fig. 1). The ROC curves showed that the AUCs (95% confidence interval) of 3 classic inflammatory markers, WBC, CRP, and ESR, were 0.632 (0.562–0.702), 0.774 (0.714–0.833), and 0.848 (0.800-0.896), respectively. The AUCs for coagulation-related tested markers, plasma fibrinogen, plasma D-dimer, PC, PCT, PDW, MPV, and PC/MPV were 0.807 (0.752–0.862), 0.755 (0.696–0.815), 0.769 (0.706–0.833), 0.785 (0.721–0.849), 0.595 (0.528–0.662), 0.722 (0.661–0.783), and 0.801 (0.744–0.858),respectively. The AUCs of these three markers (ESR, plasma fibrinogen, and PC/MPV) ranged from 0.800–0.899, which indicated that they had good diagnostic values for diagnosing infected nonunion. The AUCs for CRP, plasma D-dimer, PC, PCT, and PDW were among 0.700-0.799, indicating fair performances for diagnosing infected nonunion. Nevertheless, the diagnostic accuracy of WBC was poor, and PDW had no discriminatory capacity in diagnosing infected nonunion. Based on the Youden index, the optimal threshold, sensitivity, specificity, PPV, and NPV were 8.05×10^9/L, 38.54, 86.07, 56.92, and 74.57% for WBC; 6.35 mg/L, 67.71, 82.09, 64.36, and 61.22% for CRP; 17.5 mm/h, 72.92, 82.59, 78.26, and 67.44% for ESR; 0.92 mg/L, 60.42, 82.59, 62.37, and 81.37% for plasma D-dimer; 3.35 g/L, 63.54, 84.58, 66.30, and 82.93% for plasma fibrinogen; 294.5×10^9/L, 56.25, 90.05, 72.97,and 81.17% for PC; 0.275%, 70.83, 79.10, 78.26, and 67.44% for PCT; and 15.9%, 54.17, 56.22, 37.14, and 71.97% for PDW; 9.3 fl, 57.29, 75.62, 52.88, and 78.76% for MPV, and 31.7, 58.33, 93.53, and 81.16% for PC/MPV(Table 3).
Table 3
The diagnostic value of tested markers in patients in the two groups.
Variables | AUC (95%CI) | Optimal Cutoff Value | Sensitivity (%) | Specificity(%) | PPV (%) | NPV (%) |
WBC | 0.632 (0.562–0.702) | 8.05×10^9/L | 38.54 | 86.07 | 56.92 | 74.57 |
PC | 0.769 (0.706–0.833) | 294.5×10^9/L | 56.25 | 90.05 | 72.97 | 81.17 |
PCT | 0.785 (0.721–0.849) | 0.275% | 70.83 | 79.10 | 78.26 | 67.44 |
PDW | 0.595 (0.528–0.662) | 15.9% | 54.17 | 56.22 | 37.14 | 71.97 |
MPV | 0.722 (0.661–0.783) | 9.3 fl | 57.29 | 75.62 | 52.88 | 78.76 |
PC/MPV | 0.801 (0.744–0.858) | 31.7 | 58.33 | 93.53 | 81.16 | 82.46 |
CRP | 0.774 (0.714–0.833) | 6.35 mg/L | 67.71 | 82.09 | 64.36 | 61.22 |
ESR | 0.848 (0.800-0.896) | 17.5 mm/h | 72.92 | 82.59 | 78.26 | 67.44 |
Plasma D-dimer | 0.755 (0.696–0.815) | 0.92 mg/L | 60.42 | 82.59 | 62.37 | 81.37 |
Plasma fibrinogen | 0.807 (0.752–0.862) | 3.35 g/L | 63.54 | 84.58 | 66.30 | 82.93 |
WBC, white blood cell; PC, platelet count; PCT, plateletcrit; MPV, mean platelet volume; PDW, platelet distribution width; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; AUC, areas under the curve; CI, confidence interval; PPV, positive predictive value; NPV, negative predictive value. |
In addition, multiple combinations of plasma fibrinogen, ESR and PC/MPV were performed and their diagnostic values were assessed based on the optimal predictive cutoff values determined by using the Youden index. When using the criteria of PC/MPV 31.7 “or” Plasma fibrinogen 3.35 g/L “or” ESR 17.5 mm/h to detect infected nonunion, the sensitivity (87.50%) was highest. When using the criteria of PC/MPV 31.7 “and” Plasma fibrinogen 3.35 g/L “and” ESR 17.5 mm/h to detect infected nonunion, the specificity (99.00%) was highest (Table 4).
Table 4
The Combinational Diagnostic Values of the Tested Markers
Variables | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) |
PC/MPV or Plasma fibrinogen | 78.13 | 80.10 | 65.22 | 88.46 |
PC/MPV + Plasma fibrinogen | 41.67 | 98.01 | 90.91 | 77.87 |
PC/MPV or ESR | 82.29 | 77.61 | 63.71 | 90.17 |
PC/MPV + ESR | 48.95 | 98.51 | 94.00 | 80.16 |
Plasma fibrinogen or ESR | 84.38 | 73.63 | 60.45 | 90.80 |
Plasma fibrinogen + ESR | 52.08 | 93.53 | 79.37 | 80.34 |
PC/MPV or Plasma fibrinogen or ESR | 87.50 | 69.15 | 57.53 | 92.05 |
PC/MPV + Plasma fibrinogen + ESR | 39.58 | 99.00 | 95.00 | 77.43 |
PC, platelet count; MPV, mean platelet volume; ESR, erythrocyte sedimentation rate; PPV, positive predictive value; NPV, negative predictive value. |
Among 54 patients with coagulation-related comorbidities, there were 31 patients with infected nonunion and 23 patients with aseptic nonunion. Table 5 showed that the diagnostic values of ESR, plasma fibrinogen, and PC/MPV in patients with coagulation-related comorbidities (n = 54), including venous thrombosis (n = 20), cardiovascular and cerebrovascular diseases (n = 11), malignancy (n = 4), liver or kidney failure (n = 4), diseases of the blood system (n = 3) and infection in a site other than a fracture (n = 12) based on the optimal predictive cutoff values determined using Youden's index. PC/MPV was promising for diagnosing infected nonunion in patients with coagulation-related comorbidities (sensitivity and specificity: 77.41% and 91.30%, respectively, and PPV and NPV: 92.31% and 75.00%, respectively). Plasma fibrinogen was promising for diagnosing infected nonunion in patients with coagulation-related comorbidities (sensitivity and specificity: 64.52% and 73.91%, respectively, and PPV and NPV: 76.92% and 60.71%, respectively). However, the value of ESR was limited for diagnosing infected nonunion in patients with those patients (sensitivity and specificity: 48.39% and 52.17%, respectively, and PPV and NPV: 57.69% and 42.86%, respectively) (Table 5).
Table 5
Diagnostic Values of Tested Markers for Patients with Coagulation-Related Comorbidities
Variables | N (Infected/Aseptic) | Sensitivity (%) | Specificity (%) | PPV (%) | NPV (%) |
Plasma fibrinogen | 31/23 | 48.39 | 52.17 | 57.69 | 42.86 |
ESR | 31/23 | 64.52 | 73.91 | 76.92 | 60.71 |
PC/MPV | 31/23 | 77.41 | 91.30 | 92.31 | 75.00 |
PC, platelet count; MPV, mean platelet volume; ESR, erythrocyte sedimentation rate; PPV, positive predictive value; NPV, negative predictive value. |