Skip to main content
. 2021 Dec 16;12:762782. doi: 10.3389/fimmu.2021.762782

Table 8.

Technical recommendations and unmet questions awaiting further investigation in COVID-19-associated coagulopathy.

Further investigations on COVID-19-dependent coagulopathy Reference
Technical reccommendations
Investigations on the stability of the coagulation factors showed that storage at different temperatures, freezing/thawing, affects the activity of the factors. For instance, a change of over 10% for factor V (FV) was reported when the plasma samples were kept at room temperature only for 2 h. Additionally, factors including FII, FVII, FX, and FXII could be affected if they are kept at room temperature over 48 h. Freezing is an effective approach to store these factors; however, long-term storage affects their activity. In this regard, assessment of the impact of sample storage at −20°C showed that the prothrombin time (PT)/international normalized ratio (INR) and FIX results were unaffected only for a month, while the results of aPTT and FVIII remain unaffected for 15 days. To eliminate this pre-analytic problem, we managed to perform the experiment right at the peak when a large number of patients (both critical or severe) were hospitalized. Using this strategy, we performed our study without the need for freezing the samples. (41, 42)
A bias may occur when the results of the PT test are represented only in seconds and not using INR. This occurs because each PT kit manufactured has a unique international sensitivity index (ISI) parameter, which is used in the calculation of INR: INR = (patient PT/mean normal PT)ISI. We recommend including the INR results along with the PT expressed in seconds or at least mentioning the ISI of the used PT kits. This may be beneficial when comparing merely the PT results of different studies without considering the INR or ISI of the kits. (43)
Considering the low stability of D-dimer and fibrin degradation products (FDPs) over time, we strongly recommend performing these two tests immediately after plasma separation. (44)
If the study is aimed to be performed on a high number of individuals or it is not possible to collect samples from all individuals in a short time, in which the plasma samples should be stored until running the tests, we recommend monitoring the effect of storage on samples. For this purpose, several samples with low, normal, and high results for the PT and partial thromboplastin time (PTT) tests can be frozen with other samples in separately labeled microtubes to evaluate the test results every 12 or 24 h by comparing the results with those from plasma samples before freezing. (45)
Considering that pregnant women with physiological pregnancy have higher levels of D-dimer and fibrinogen, we recommend not including them as controls. Additionally, including them in the patient group may result in exaggerated results. (46)
Fibrinogen levels may vary widely in several bio/pathologic situations, i.e., rise after menopause, rise in diabetes and hypertension, or decrease in alcoholics. We recommend considering such situations in the questionnaire to simply exclude unfit individuals. (47)
Considering that PO2 pressure is a critical factor in placing patients in the critical (CTL) and severe (SVR) groups and that it may vary during a single day in COVID-19 patients, we suggest placing patients with the lowest values into the CTL group and those with the highest into the SVR group and avoiding placing patients with PO2 values near the cutoff. (48)
Unmet questions
C4b-BP has been reported to regulate proteins C and S. Since our results magnified the role of these two regulatory proteins in COVID-19-dependent coagulopathy, investigation of the association between the activity of proteins C and S and the concentration of C4b-BP can be helpful. (49, 50)
The links between gene mutation and polymorphisms in coagulation regulatory proteins and coagulation disorders have been reported. Studying the association between the SNPs of proteins C and S and ATIII with the prognosis of COVID-19 in patients with coagulopathy could be beneficial. (51)
Heparin therapy is widely recommended in patients with COVID-19. Considering that it acts as the cofactor for ATIII to inhibit thrombin and factor Xa, an investigation on the impact of heparin therapy on thrombin time (TT) and factor Xa activity may be an interesting theme for further research. (8)
Proteins C and S regulate the conversion of V to Va and VIII to VIIIa. We suggest investigating these 6 factors for their possible association with the fate of critically ill patients. (52)