Baseline characteristics of study participants are depicted in Table:1.
Table: 2 summarizes Serum Procalcitonin (PCT) levels in relation to sepsis screen in Group 1 and Group 2. 154 subjects (62.34%) were PSS equal to two and 93 subjects (37.66) were PSS more than two. In Group 1, Out of 247; sepsis screen was positive (≥2) in 52.23% subjects and negative (<2) in 47.77% subjects. In group 2, 17 subjects (42.5%) were sepsis screen negative and 23 subjects (57.5%) were sepsis screen positive.
Serum Procalcitonin (PCT) levels in Group 1 and group 2 newborns according to sepsis screen and blood culture are depicted in Table 2 &3.
Serum Procalcitonin (PCT) levels in Group 1 newborns according to sepsis screen and blood culture- For detecting probable sepsis newborns PCT had a test sensitivity 47.1%, a higher specificity 86.4% and low PPV of 33.3%. overall diagnostic accuracy was found to be 81.5% indicating the PCT is a good test for diagnosing EOS (p value< 0.002). In probable sepsis serum PCT estimation has a high NPV (91.9%), this is the peak of high specificity of this test for excluding neonatal sepsis. On comparing Group-a, and Group c the PPV was 69.2% and NPV was 57.3% which only give that estimation of serum PCT values have reasonably good sensitivity (Sn) and specificity (Sp). For detecting probable sepsis (SS positive, blood culture negative) newborns, PCT has a sensitivity of 47.1%, indicating that it can only correctly identify 47.1% of these patients. A high specificity of 86.4% indicates that PCT is good for excluding these cases. A low PPV of 33.3% indicates that if PCT is raised, then only 33.3% patients will have SS positive, blood culture negative. A high NPV indicates that if PCT is low then 91.9% patients will not have SS positive, blood culture negative. Overall diagnostic accuracy is 81.5%, indicating that PCT is a good test for identifying these patients (p <0.05).
Serum Procalcitonin (PCT) levels in Group 2 newborns according to sepsis screen and blood culture- In group 2; The sensitivity (Sn), specificity (Sp) and positive predictive value (PPV) and negative predictive value (NPV) and diagnostic accuracy (DA) and p value of Group b were respectively 61.5%, 47.1%, and 47.1%, 61.5% and 53.3%, p value>0.334, statistically not significant between Group a (clinical sepsis) and Group b (Probable sepsis) for PCT. Out of 10 subjects in Group c, 40% subjects had Serum PCT<0.5 ng/mL and 60% subjects had values ≥0.5 ng/mL. The sensitivity (Sn), specificity (Sp) and positive predictive value (PPV) and negative predictive value (NPV) and diagnostic accuracy (DA) and p value were respectively 60%, 47.06% and 40%,66.7% and 51.8%, p value>0.721 of Group c, statistically not significant between Group a (clinical sepsis) and Group c (Proven sepsis) for PCT.
Relationship of Serum Procalcitonin (PCT) levels in Group 1 and 2 newborns with blood culture are depicted in Table 3.
Serum Procalcitonin (PCT) levels in Group 1 newborns according blood culture- Serum PCT equal or more than 0.5 ng/mL was found in 31.15% cases of blood culture positive subjects. The sensitivity, specificity and PPV and NPV and diagnostic accuracy (DA), p value respectively was 44.4%,86.4% and 33.3%,91.1% and 80.09%, p value <0.005(s), statistically significant for PCT in cord blood. For detecting blood culture positive patients, PCT has a sensitivity of 44.4%, indicating that it can only correctly identify 44.4% of these patients. A high specificity of 86.4% indicates that PCT is good for excluding these cases. A low PPV of 33.3% indicates that if PCT is raised, then only 33.3% patients will have blood culture positive. A high NPV indicates that if PCT is low then 91.9% patients will not have blood culture positive. Overall diagnostic accuracy is 80.9%, indicating that PCT is a good test for identifying these patients in cord blood (p <0.05).
Serum Procalcitonin (PCT) levels in Group 2 newborns according to blood culture- However, venous blood (Group 2) PCT failed to demonstrate similar results. in Group 2(n=40); Blood culture was positive in 25% cases. Serum PCT levels <0.5 ng/mL in 4 (40%) subjects and ≥0.5 ng/mL in 6 (60%) subjects out of 10 blood culture positive subjects. Serum PCT levels < 0.5 ng/mL in 13 (43.44%) and ≥0.5 ng/mL in 17 (56.66%) subjects, out of 30 blood culture negative subjects. (Table 4). Venous blood serum PCT levels were increased in 60% of blood culture positive newborns and 56.66 % in blood culture negative subjects. P value= 0.853 is not significant. Diagnostic utility of venous blood serum PCT showing sensitivity, specificity, PPV, NPV and Diagnostic accuracy with blood culture taken as a gold standard were 60%,43.3%,26.1%,76.5% and 47.5%. P value is not significant for PCT in venous blood; therefore, it cannot replace the blood culture as gold standard test.
Comparison of Receiver operating characteristic curve (ROC) of PCT, CRP, TLC, ANC, m-ESR and Platelets for diagnosis of early onset of sepsis in Group 1 newborns (Figure:1): On Receiver operating characteristic curve (ROC) analysis, cord blood serum PCT, TLC, ANC and platelet showed statistically significant area under curve (AUC) value ranging from 0.587 to 0.624 (95% CI). P value is highly significant for PCT and TLC, significant in ANC and platelet.
Comparison of Receiver operating characteristic curve (ROC) of PCT, CRP, TLC, ANC, m-ESR and Platelets for diagnosis of early onset of sepsis in Group 2 newborns (Figure:2): On ROC curve analysis, venous blood m-ESR showed statistically significant area under curve (AUC)value 0.686 significant (95%CI) and p value is significant (0.046) for m-ESR. Serum PCT, CRP, TLC and Platelets did not show significant area under curve (AUC >0.5).
On ROC curve analysis, area under curve (AUC) value were found to be significant for PCT, TLC, ANC and platelet counts (AUC>0.5 values between 0.587 to 0.624 - 95% confidence interval); PCT and TLC had the highest diagnostic value (p value<0.001 and p < 0.004) and ANC & Platelets also had significant diagnostic values (p<0.021 and p<0.018). speaking about their diagnostic value for EOS in cord blood samples, while in venous blood sample only micro-ESR had shown significant area under curve value more than 0.5 (0.686 -95% CI and significant p value 0.046) while no other parameters had shown significant area under curve (AUC<0.5). (Figure-1,2)
In summary, slightly higher percentage positive cut off value of PCT (29.04%) was observed in newborns with strongly positive perinatal sepsis screen compared with positive perinatal sepsis score that is 21.43%, the difference was statistically not significant. Newborns with sepsis screen positive status had shown a significantly higher percentage (34.11%) having PCT value equal or more 0.5ng/mL, while only 13.55% of sepsis screen negative newborns had shown positive cutoff value. Our results show a significant role of PCT in diagnosing early onset of sepsis (EOS) in cord blood samples, but PCT estimation failed to demonstrate similar diagnostic value in newborns of Group 2 (p value=0.859). For detecting probable sepsis newborns had a PCT test sensitivity 47.1%, a higher specificity 86.4% and low PPV of 33.3%. overall diagnostic accuracy was found to be 81.5% indicating the PCT is a good test for diagnosing EOS (p value< 0.002). However, PCT estimation failed to demonstrate similar results in venous blood samples taken from neonatal sepsis. Cord blood PCT was increased in 32.15% blood culture positive newborns and 17.77 % in blood culture negative subjects and P value (p<0.005) is highly significant. Diagnostic utility of Cord blood serum PCT showing sensitivity, specificity, PPV, NPV and Diagnostic accuracy with blood culture taken as a gold standard were 44.4%,86.4%,33.3%,91.1% and 80.9%. However, venous blood (Group 2) PCT failed to demonstrate similar results. On ROC curve analysis, area under curve (AUC) value were found to be significant for PCT, TLC, ANC and platelet counts (AUC>0.5) speaking about their diagnostic value for EOS in cord blood samples, while in venous blood sample only micro-ESR had shown significant area under curve value more than 0.5 while no other parameters had shown significant area under curve (AUC<0.5).