Diagnosis of infection post solid organ transplantation should be as early as possible, as the delay of antimicrobial administration will lead to potentially long term effects on the morbidity and mortality. While initiation of antimicrobials to treat colonization will expose both patients & centers to resistance, increase cost, and drug side effects.4
PCT is used as a marker of early bacterial translocation in some group of patients.6 However, in solid organ transplantation (SOT), PCT levels may be affected by other factors e.g. the surgical procedure, underlying disease, and immunosuppression used that interfere with its interpretation & makes it more challenging in the transplant group.7-9
Procalcitonin is the precursor molecule of human calcitonin, its molecular weight is about 13KD & with no hormonal activity.10 In normal individuals, it is present in very low concentration about 0.5ng/ml. However, during bacterial infection & multi-organ failure, it will exceed this value to reach 100ng/ml.11 Procalcitonin has half-life about 24hours while calcitonin has a shorter half-life about 10-20 minutes.10
Regarding the primary outcome of the study is to determine the association between rising serum procalcitonin and infectious complications in immunosuppressed LDLTRx.
So, the patients were classified into the positive culture group & the negative one then retrospectively following up the sepsis laboratory variables in each group (mainly TLC, Band cells%, CRP and PCT) to allow finding simple, rapid marker that would be suitable post LDLTX to diagnose clinically significant infections.
PCT levels were higher with statistically significant (P-value < 0.05) in the positive culture group from day one till day 5 postoperative. The cutoff value that was highly specific to infection, ≥ 9ng/ml (specificity of 83.7% on day one postoperative and specificity was highest on day three 90.7%).
Early post LTx, the cutoff value of PCT that would be associated with infection has not been defined, depending on the type of allograft and the extent of the surgery, so PCT levels may increase or remain stable after transplantation.12
Perrakis et al. found that post LTx, PCT values > 5ng/mL increased 11.7 times the odds of developing complications e.g. infectious complications, renal failure, bleeding, and respiratory failure.13
As the literature in the setting of liver or kidney transplantation is not extensive, so, in heart transplant recipients, PCT with cutoff values > 0.6ng/ml was correlated with local infection while in multiple infections & sepsis PCT levels were substantially elevated to (7.3-22.4ng/ml).14
Chen et al. showed that PCT can be used to predict catheter-related bloodstream infections post liver transplantation (LTx), where the PCT values > 3.1ng/ml had a sensitivity of 72% and specificity of 87% to predict the infection.15
Study of lung transplant patients, using the PCT to differentiate between colonization & infection where PCT was mildly elevated in colonization with cutoff value <2 and >0.5ng/ml.16,17
Kunz et al. measured PCT immediately before and daily after liver transplantation in 22 patients and found that all patients had increased PCT levels without clinical signs of infection.18
Prieto et al. reported a cutoff value of 1.92ng/mL as a predictor for both infectious and non-infectious complications with a sensitivity of 95.6% and specificity of 89.5%, although those who suffered complications had worse preoperative criteria and higher Child–Pugh scores.19
Regarding to PCT dynamics, in the study of heart and lung recipients, PCT level was high in the first 24hours postoperative & it remained high in those patients who suffered infectious complications,20-22 PCT Level reached (mean ±SD),(54.6 ±8.8ng/ml) in patients with complications, compared to (9.1 ±9.3ng/ml) in patients without complications. At the same time TLC and CRP could not differentiate between patients with infections from those without.20,21 Thus, it is advised to follow PCT level after 24h reading post-transplant.
In this study, TLC was higher in the positive culture group and statistically significant (P-value < 0.05) from day one till the fourth day postoperative. TLC cutoff value of ≥ 17.3/mm3on day one; had the specificity of > 90%. Therefore & according to our sample, both PCT & TLC can help early rapid diagnosis of infection till culture results will be available. While both CRP and band cells% were not differ in between the positive culture group and the negative one.
Although CRP results were high in both groups of culture results but were not statistically significant, this rise could be related to the surgery, underlying disease, or blood transfusion.
CRP level and leukocyte counts could not be able to differentiate between infectious and non-infectious complications at any time point.19,20
Regarding outcome at PCT cutoff value 0f ≥9ng/ml, ICU stay on day three was correlated with that cutoff & was statistically significant (P-value= 0.05). While hospital stay was not differ at either PCT cutoff value of ≥ 9ngml or < 9ng/ml & it might be due to the small number of patients enrolled.
Study done for heart transplant recipients, found that increased PCT level to > 10ng/mL was associated with poor outcomes.22
While following the demographic, anesthetic and operative variables; the amount of blood loss and amount of blood transfused were correlated with the positive culture results and they were statistically significant (P- value= 0.001 & 0.029 respectively). These results matches another study done where dominant elective abdominal surgeries were included and showed that the number of units of blood transfused was directly proportional to the incidence of complications and mortality; infectious complications represented the highest incidence 36.3%.23
Therefore, the surgical and anaesthetic techniques that aid to limit blood loss and blood transfusion intraoperative will positively affect the incidence of postoperative infectious complications.