Prolonged Activated Partial Thromboplastin Time

Features of clinical and laboratory diagnosis of rare coagulopathy – acquired hemophilia

Introduction. The formation of circulating autoantibodies capable of inhibiting factors of the blood coagulation system is accompanied by the occurrence of spontaneous and/or post-traumatic bleeding in patients without a history of previous disorders of the hemostasis system. One of the reasons for the development of such conditions is acquired hemophilia.

Aim – to present algorithms for laboratory diagnosis of acquired hemophilia.

Main findings. Primary diagnosis and control of therapy of the disease are carried out based on the results of coagulation studies, the decoding and interpretation of which often causes difficulties due to the low awareness of doctors about the algorithms for laboratory diagnosis and tactics for managing patients. In acquired hemophilia there is no direct relationship between the results of laboratory tests and the clinical manifestations of the disease, which is determined by the kinetics of the interaction of autoantibodies with blood coagulation factor (F) VIII. There is a «false» in vitro decrease in the activity of factors of the internal pathway (FIX, FXI and FXII), associated with the effect of a rapid inhibitor in high titers. An important laboratory task is the determination of lupus anticoagulant, which makes it difficult to timely diagnose and verify the diagnosis.

Concomitant factor VIII inhibitor and lupus anticoagulant in an asymptomatic patient

Acquired hemophilia A, caused by autoantibodies that bind to and neutralize the activity of coagulation factor VIII (FVIII), almost universally presents as a severe bleeding diathesis. Lupus anticoagulants (LAs), autoantibodies directed against phospholipids or protein-phospholipid complexes, manifest clinically with an increased risk of thrombosis. While these autoantibodies are uncommon, the distinctive clinical presentation in conjunction with the typical laboratory findings often enable straightforward identification of the underlying autoantibody. However, the presence of a concomitant acquired FVIII inhibitor and LA is exceedingly rare with fewer than 20 documented cases. All prior patients presented with life-threatening hemorrhage, thrombosis, or both, prompting comprehensive hematologic evaluation and subsequent identification of the pathologic antibodies. We describe a novel case of a patient with no signs of hemorrhage or thrombosis who was incidentally found to have both a FVIII inhibitor and LA during evaluation of a prolonged partial thromboplastin time (PTT). This finding resulted in FVIII inhibitor-directed management, including immunosuppressive therapy. The unique presentation of an incidental FVIII inhibitor and LA in an asymptomatic patient without thrombotic or bleeding complications highlights the potential challenge in elucidating the etiology of a prolonged PTT, as LAs and FVIII inhibitors both prolong the PTT, and each entity can interfere with assays designed to detect the presence of the other autoantibody. This case underscores the importance of recognizing that patients with major underlying disturbances in their hematologic physiology, but in whom clinical symptoms have yet to manifest, may potentially be overlooked until such symptoms are evident.

Characteristics of Acquired Inhibitors to Factor VIII and Von Willebrand Factor Secondary to Systemic Lupus Erythematosus: Experiences From a Chinese Tertiary Medical Center

OBJECTIVE

Because acquired hemophilia (AH) is a rare entity in systemic lupus erythematosus (SLE), we aimed to investigate the clinical features of SLE-related AH in Chinese patients.

METHODS

This is a medical records review study carried out at a large tertiary care hospital in China from years 1986 to 2018. We searched the case database in Peking Union Medical College Hospital using the International Classification of Diseases. The clinical data on SLE-related AH patients were collected.

RESULTS

A total of 9282 SLE patients had been hospitalized. Six female SLE-related AH patients were identified. Four patients had acquired hemophilia A (AHA), and 2 patients had acquired von Willebrand syndrome. Their mean age was 33.67 ± 13.77 years. Five patients had active disease. The mean SLE disease activity index measured at the time of diagnosis of AH was 10.50 ± 5.28. The average level of activated partial thromboplastin time was 86.5 seconds. Coexistence of secondary antiphospholipid syndrome and AHA was found in one case, and pulmonary embolism was observed 3 years later. After immunosuppressive therapy and symptomatic treatment, an overall remission rate of 83.3% was achieved.

CONCLUSIONS

The frequency of SLE-related AH was low. The development of AH in SLE patients frequently occurs with active disease. The AH could be the first clinical presentation of SLE. Secondary antiphospholipid syndrome and AHA could appear in the same SLE patient. Early and aggressive treatment contributes to a favorable prognosis.

Lupus anticoagulant in children – a confounding factor in diagnosis and targeted therapy

Introduction: Lupus anticoagulant (LAC) belongs to a heterogeneous group of antibodies directed against negatively charged phospholipid-binding proteins, inhibiting phospholipid-dependent reactions. We assessed the frequency, etiological background, clinical and biological expression as well as the appropriate management and outcome of LAC in a pediatric population.

Patients and methods: We included 19 pediatric patients diagnosed with a positive LAC test during a period of 1 year. LAC detection was carried out according to the ISTH/SCC guidelines 2012. Coagulometric assays were performed in order to check for coagulation factor activities. The presence of specific inhibitors has been tested by the Bethesda assay.

Results: LAC was positive in 0.4% of the patients monitored for increased activated partial thromboplastin time (aPTT) during the study period of 1 year. In contrast to the asymptomatic clinical image presented by the majority of our patients, the biological picture was dominated by an elevated aPTT (79 %), the aPTT ratio correlating significantly with the strength of LAC. In 58 % of the patients LAC became negative within 12 weeks, in another 4 (21%) patients within 20 weeks, whereas in 4 (21%) patients LAC remained positive throughout the follow-up.

Conclusion: Albeit usually innocent in asymptomatic patients, LAC needs to be seriously taken into consideration from the diagnostic point of view in order to avoid dangerous therapeutic attitudes..

Unexpected, isolated activated partial thromboplastin time prolongation: A practical mini-review

A common inquiry in coagulation laboratories is how to interpret an unexpected, isolated prolonged activated partial thromboplastin time (APTT). In this context, isolated means together with a normal prothrombin time (PT) and/or normal international normalized ratio (INR). This finding may lead to contact with laboratory doctors for further advice on a diagnostic strategy. Occasionally, the need for a diagnostic algorithm can be subacute, where surgery has to be postponed until an explanation for the isolated, prolonged APTT has been established. Activated partial thromboplastin time as a coagulation test was developed to monitor patients with hemophilia. Different APTT reagents display considerable differences in their sensitivity to deficiencies of coagulation factors. An isolated, prolonged APTT is seen in (a) individuals/patients with lupus anticoagulants, (b) patients in treatment with anticoagulants, mainly heparin, and (c) patients with deficiencies of specific coagulation factors. In this tutorial review, we summarize what may cause an isolated prolonged APTT and we present a simple diagnostic algorithm to differentiate between lupus anticoagulants (common) and factor deficiencies (rare). The identification of an isolated prolonged APTT as well as the underlying cause can be of the utmost importance in ensuring the correct therapeutic follow-up.

A combined approach using global coagulation assays quickly differentiates coagulation disorders with prolonged aPTT and low levels of FVIII activity

Patients with mild/moderate hemophilia (H)A, acquired HA (AHA) and lupus anticoagulants (LA), have prolonged aPTTs with low levels of factor (F)VIII activity, but the differentiation of these disorders is complex and time consuming. We established an approach to quickly differentiate these disorders using comprehensive coagulation tests. Patients' plasmas with mild/moderate HA, AHA, LA without anti-phospholipid syndrome [LA-APS(-)], and LA with APS [LA-APS(+)] were examined using clot waveform analysis (CWA) and thrombin generation test (TGT). Activated protein C (APC) sensitivity was assessed by TGT. CWA revealed similarly prolonged clot times in all groups [NP/mild/moderate HA/AHA/LA-APS(-)/LA-APS(+); 33 ± 1/82 ± 12/116 ± 44/90 ± 29/96 ± 15 s] but significantly different decreased maximal coagulation velocity (3.1 ± 0.1/1.3 ± 0.3/0.9 ± 0.5/1.6 ± 0.3/2.2 ± 0.5). In TGT, AHA group demonstrated severely reduced peak-thrombin levels (362 ± 23/170 ± 27/49 ± 21/158 ± 75/158 ± 99 nM), whilst both LA groups markedly prolonged lag times (4.5 ± 0.3/5.0 ± 0.4/4.7 ± 0.8/12.5 ± 7.7/28.8 ± 11.8 min), suggesting that AHA could be readily identified, but the different LA sub-types failed to be classified. An APC sensitivity demonstrated that 'normalized' APC-induced levels of peak thrombin in LA-APS(+) were significantly lower relative to LA-APS(-) (normalized %inhibition; 5 ± 7/42 ± 39 %). Our studies confirmed that %inhibition by APC was significantly decreased in NP preincubated with purified IgGs from LA-APS(+) compared to LA-APS(-), facilitating differentiation between LA groups. A combined approach using CWA and TGT could be a useful means of differentiating coagulation disorders with prolonged aPTT.