Validation of the PLASMIC score, a clinical prediction tool for thrombotic thrombocytopenic purpura diagnosis, in Chinese patients

Case report: Thrombotic thrombocytopenic purpura in a pregnant woman with lupus membranous nephropathy: a diagnostic challenge

A 27-year-old female at 20th week of pregnancy was admitted with edema, foamy urine, but normal blood pressure. Her blood count was normal, she had proteinuria of 3 g/day, creatinine 0.4 mg/dl, albumin 2.4 g/dl, and cholesterol 355 mg/dl. Antinuclear antibodies 1/160, but Anti-DNA, anticardiolipin antibodies and lupus anticoagulant were negative, with normal serum C3 and C4. A renal biopsy showed secondary membranous glomerulopathy, most likely lupus class V pure. Steroids, azathioprine, and aspirin were initiated, up to 28 weeks of pregnancy, when she developed severe hypertension, photopsia, headache, anasarca, extensive bruising of the extremities, severe anemia, thrombocytopenia, and creatinine rose to 2.09 mg/dl with preserved diuresis. A female infant, 1045 grams, was delivered by emergency caesarean section. Following the surgery, she experienced diplopia, dysarthria, bradypsychia, and sensory alterations in the lower extremities, necessitating emergency hemodialysis due to pulmonary congestion. Blood smear revealed schistocytes, LDH elevated at 1148 IU/L, while transaminases and liver function remained normal, suggesting thrombotic thrombocytopenic purpura. ADAMTS13 revealed 6% activity with the presence of inhibitor. Mycophenolate and daily plasmapheresis with fresh frozen plasma replacement yielded unsatisfactory response, unaffected by the addition of methylprednisolone pulses and rituximab. Eventually, intravenous cyclophosphamide was introduced, resulting in complete hematological remission and normalization of ADAMTS13, however dialysis-dependence persisted and four years later, right renal cancer prompted bilateral nephrectomy. After a total follow-up of six years, she remained free of neoplastic recurrence and lupus activity, receiving prednisone and hydroxychloroquine. The differential diagnosis of microangiopathic syndrome in a pregnant lupus patient is discussed.

Potential modifications of the PLASMIC scoring system for predicting thrombotic thrombocytopenic purpura: Sometimes, less is more

INTRODUCTION

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening occlusive disease of the microcirculation characterized by systemic platelet plugs, organ ischemia, deep thrombocytopenia, and fragmentation of erythrocytes. One of the widely used scoring system to determine the clinical probability of TTP is the PLASMIC scoring system. This study aimed to evaluate the contribution of PLASMIC score modifications to sensitivity and specificity in patients with microangiopathic hemolytic anemia (MAHA) undergoing plasma exchange with a prediagnosis of TTP at our center.

MATERIALS AND METHODS

The data of patients who were hospitalized with a previous diagnosis of MAHA and TTP and underwent plasma exchange at Bursa Uludag University, Faculty of Medicine, Department of Hematology between January 2000 and January 2022 were retrospectively analyzed.

RESULTS

Overall, 33 patients (including 15 and 18 with and without TTP, respectively) were included in this study. Receiver operating characteristic (ROC) analysis revealed that the area under the curve (AUC) for the original PLASMIC score was 0.985 (95% confidence interval [95% CI]: 0.955-1.000), and AUC for the PLASMIC score without mean corpuscular volume (MCV) was 0.967 (95% CI: 0.910-1.000), which is close to the original AUC. With the removal of MCV from the scoring system, the sensitivity decreased from 100% to 93%, whereas the specificity increased from 33% to 78%.

CONCLUSIONS

Based on the results of this validation study, removing MCV from the PLASMIC score led to the categorization of eight non-TTP cases in the low-risk category, and this could avoid unnecessary plasma exchange. However, in our study increasing the specificity was at the expense of the sensitivity by missing one patient with this new scoring system without MCV. Further multicenter studies with large sample sizes are required owing to the fact that different parameters may be effective in TTP prediction among different populations.

A validation and modification of PLASMIC score by adjusting the criteria of mean corpuscular volume and international normalized ratio

BACKGROUND

The PLASMIC score was developed for distinguishing thrombotic thrombocytopenic purpura (TTP) from other types of thrombotic microangiopathy. However, two components of the PLASMIC score, mean corpuscular volume (MCV) and international normalized ratio (INR), showed non-significant differences between TTP and non-TTP patients in previous validations. Here, we validate the PLASMIC score and aim to modify it by adjusting the criteria of MCV and INR.

MATERIALS AND METHODS

A retrospective validation of suspected TTP patients was performed by reviewing electronic medical records from two medical centers in Taiwan. The performance of different modified types of the PLASMIC score was carried out.

RESULTS

Among 50 patients included in the final analysis, 12 were diagnosed with TTP based on deficiency of ADAMTS13 activity and clinical judgement. When stratified by high (score ≥ 6) and low-intermediate risk (score < 6), the positive predictive value (PPV) of the PLASMIC score to predict TTP was 0.45 (95% confidence interval [CI]: 0.29-0.61). The area under curve (AUC) was 0.70 (95% CI: 0.56-0.82). When adjusting the criteria of the PLASMIC score from MCV < 90 fL to MCV ≥ 90 fL, the PPV increased to 0.57 (95% CI: 0.37-0.75). The AUC was 0.75 (95% CI: 0.61-0.87). When adjusting the INR from >1.5 to >1.1, the PPV increased to 0.56 (95% CI: 0.39-0.71). The AUC was 0.81 (95% CI: 0.68-0.90).

CONCLUSION

MCV ≥ 90 fL and/or INR > 1.1 might be suitable modifications for PLASMIC score but should be validated in a larger sample size.

Pregnancy-associated thrombotic thrombocytopenic purpura complicated by Sjögren's syndrome and non-neutralising antibodies to ADAMTS13: a case report

Background

Thrombotic thrombocytopenic purpura (TTP) is a severe and life-threatening disease. Given its heterogeneous clinical presentation, the phenotype of TTP during pregnancy and its management have not been well documented.

Case presentation

We report here a 25-year-old woman, G1P0 at 36 weeks gestation, who developed severe thrombocytopenia and anemia. She was performed an emergent caesarean section 1 day after admission because of multiple organ failure. As ADAMTS 13 enzyme activity of the patient was 0% and antibodies were identified by enzyme-linked immunosorbent assay, she was diagnosed as acquired thrombotic thrombocytopenic purpura (aTTP). Furthermore, asymptomatic primary Sjögren’s syndrome was incidentally diagnosed on screening. After treatment with rituximab in addition to PEX and steroids, the activity of the ADAMTS 13 enzyme increased significantly from 0 to 100%.

Conclusions

To the best of our knowledge, this is the first case report of concomitant TTP and asymptomatic Sjögren’s syndrome in a pregnant woman. It highlights the association between pregnancy, autoimmune disease, and TTP. It also emphasizes the importance of an enzyme-linked immunosorbent assay in the diagnosis and rituximab in the treatment of patients with acquired TTP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04167-9.

Thrombotic thrombocytopenic purpura complicated with acute aortic dissection: A case report

RATIONALE

Thrombotic thrombocytopenic purpura (TTP) is a critical thrombotic microangiopathy involving multiple organs. To the best of our knowledge, there are no reports of TTP complicated by acute aortic dissection.

PATIENT CONCERNS

We herein described a 53-year-old male with TTP who did not have a significant medical history. After immediate plasma exchange and glucocorticoid therapy, the patient's clinical condition improved. However, the patient suddenly experienced chest pain with elevated blood pressure.

DIAGNOSES

Computed tomography angiography suggested acute type B aortic dissection.

INTERVENTIONS

The patient was immediately transferred to the cardiac aortic surgery department for thoracic aortic endovascular repair.

OUTCOMES

The patient was discharged after successful thoracic aortic endovascular repair. Unfortunately, 3 months later, the patient experienced chest and back pain at home and died suddenly, possibly due to the recurrence of aortic dissection.

LESSONS

Even if patients have no identifiable risk factors, physicians should be aware of this rare and life-threatening acute complication of TTP, which may have multiple causes, including preexisting connective tissue disease, abnormal blood pressure fluctuations, and increased risk of hemorrhage. Early identification and timely treatment of acute aortic dissection are critical for improving prognosis.

Proteinuria Increases the PLASMIC and French Scores Performance to Predict Thrombotic Thrombocytopenic Purpura in Patients With Thrombotic Microangiopathy Syndrome

Introduction

PLASMIC and French scores have been developed to help clinicians in the early identification of patients with thrombotic thrombocytopenic purpura (TTP). Nevertheless, the validity of these scores in thrombotic microangiopathy (TMA) cohorts with low TTP prevalence remains uncertain. We aimed to evaluate their diagnostic value in routine clinical practice using an unselected cohort of patients with TMA. We also analyzed the value of adding proteinuria level to the scores.

Methods

We retrospectively included all patients presenting with a biological TMA syndrome between January 1, 2008, and December 31, 2019, in a tertiary hospital. TMA etiology was ascertained, and scores were evaluated. Modified scores, built by adding 1 point for low proteinuria (<1.2 g/g), were compared with original scores for TTP prediction.

Results

Among 273 patients presenting with a full biological TMA syndrome, 238 were classified with a TMA diagnosis. Complete scores and proteinuria level were available in 134 patients with a TTP prevalence of 7.5%. Area under the receiver operating characteristic curve (AUC) of PLASMIC and French scores for TTP diagnosis was 0.65 (0.46–0.84) and 0.72 (0.51–0.93), respectively. AUC of modified PLASMIC and French scores was 0.76 (0.59–0.92) (P = 0.003 vs. standard score) and 0.81 (0.67–0.95) (P = 0.069 vs. standard score), respectively. Specificity, positive predictive value (PPV), and positive likelihood ratio of high-risk scores were significantly improved by adding proteinuria level.

Conclusion

PLASMIC and French scores have low predictive values when applied to an unselected TMA cohort. Including proteinuria level in the original scores improves their performance for TTP prediction.

Comparison of Clinical Scoring Systems in the Management of Patients with Microangiopathic Hemolytic Anemia and Thrombocytopenia

Objective:

Several clinical scoring systems have been developed for the differential diagnosis of thrombotic microangiopathies (TMAs), all to predict and identify patients with ADAMTS13 deficiency and to start treatment as soon as possible. The first scoring system in this regard was the Bentley score, and the French score and PLASMIC score were developed afterwards.

Materials and Methods:

We aimed to evaluate the laboratory parameters and clinical features of patients who underwent plasma exchange with a prediagnosis of TTP at our clinic between 2007 and 2019 and whose ADAMTS13 enzyme levels were measured and to compare the findings with the scoring systems.

Results:

Data of 35 patients were evaluated. Twelve patients were evaluated as high risk according to all three scoring systems. A statistically significant relation was observed between all three scoring systems and ADAMTS13 levels.

Conclusion:

A moderate correlation was found between all three scoring systems and ADAMTS13 levels. We observed similar potential strength of all three scoring systems to predict TTP among other TMAs and we conclude that they are applicable in daily practice.

Reduced sensitivity of PLASMIC and French scores for the diagnosis of thrombotic thrombocytopenic purpura in older individuals

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder characterized by thrombocytopenia, microangiopathic hemolysis, and ischemic organ failure. The PLASMIC and French TTP scores can help guide clinical decisions when ADAMTS13 testing is not immediately available. Older individuals often present atypically, but the impact of age on these tools is not known.

STUDY DESIGN AND METHODS

We calculated the sensitivity and specificity of the PLASMIC and French TTP scores in patients enrolled in the Johns Hopkins thrombotic microangiopathy (TMA) registry.

RESULTS

Of 257 patients with TMA enrolled in the registry, we excluded patients less than 18 years of age (n = 19), with prior TMA (n = 81) or who initially presented at another hospital (n = 25). The remaining 132 patients (75 with TTP and 57 with other TMA) were analyzed. Sensitivity of a French score of 2 decreased with age and was 72.2%, 61.5%, and 46.2% for ages 18 to 39, 40 to 59, and ≥ 60 years old, respectively. A PLASMIC score ≥ 5 had higher sensitivity than the French score but this also decreased with age; sensitivity was 91.4% (95% confidence interval [CI], 76.9-98.2), 78.3% (95% CI, 56.3-92.5), and 76.9% (95% CI, 46.2-95.0) for patients 18 to 39, 40 to 59, and ≥ 60 years old, respectively. Older patients had higher platelet counts and serum creatinine than the youngest group, contributing to the loss in sensitivity.

CONCLUSION

The PLASMIC and French TTP scores have reduced sensitivity at age ≥ 60 years and are less reliable in identifying TTP in older patients. A high index of suspicion and availability of rapid ADAMTS13 assays is required to correctly diagnose all patients with TTP.

Validation of the PLASMIC score for predicting ADAMTS13 activity <10% in patients with suspected thrombotic thrombocytopenic purpura in Alberta, Canada

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic microangiopathy (TMA) that requires prompt plasma exchange. Clinical prediction tools may facilitate decision-making in institutions with delayed turnaround time or limited access to ADAMTS13 assays. The PLASMIC score and Bentley score have been shown to predict severe ADAMTS13 deficiency with excellent sensitivity and specificity.

OBJECTIVES

To validate the PLASMIC score using a population of suspected TTP, and evaluate its discriminatory power in predicting severe ADAMTS13 deficiency in comparison with Bentley score and clinical gestalt.

METHODS

Adults presenting with suspected TTP in Alberta, Canada between 2008 and 2018 with available ADAMTS13 results were included. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for PLASMIC score, Bentley score and clinical gestalt. Receiver operator characteristics analysis assessed the performance of the scoring systems.

RESULTS

Among 163 individuals with suspected TTP, ADAMTS13 activity was available in 117 (72%). Severe ADAMTS13 deficiency <10% was present in 62 (53%). High-risk PLASMIC score (≥6) predicted severe ADAMTS13 deficiency with a sensitivity of 81.7%, specificity 71.4%, PPV 75.4% and NPV 78.4% (c-statistic 0.80). Intermediate-high risk Bentley score (≥20) had a lower sensitivity (59.5%) and higher specificity (93.9%) with similar c-statistic (0.77). Clinical gestalt had similar sensitivity as PLASMIC score but very low specificity (16.1%).

CONCLUSIONS

Both PLASMIC and Bentley scores had good discriminatory power in identifying severe ADAMTS13 deficiency in a Canadian TMA population compared to clinical gestalt. Integration into institutional clinical pathways may help supplement clinical judgment and reduce costs.

Diagnostic accuracy of the PLASMIC score in patients with suspected thrombotic thrombocytopenic purpura: A systematic review and meta-analysis

BACKGROUND

The PLASMIC score was developed to identify patients with thrombotic microangiopathy who are most likely to have immune thrombotic thrombocytopenic purpura (TTP) and benefit from therapeutic plasma exchange (TPE). PLASMIC scores of 0-4, 5, and 6-7 are said to correspond to low, intermediate, and high probability of TTP, respectively.

STUDY DESIGN AND METHODS

We conducted a systematic review and meta-analysis on the diagnostic accuracy of the PLASMIC score in adults with suspected TTP. We evaluated the sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of PLASMIC score thresholds of ≥5 and ≥6. Study quality was appraised using the QUADAS-2 tool.

RESULTS

We identified 13 eligible studies, which collectively enrolled 970 patients. The median prevalence of TTP among eligible studies was 35%. The sensitivity and specificity of a PLASMIC score ≥5 was 0.99 (95% confidence interval [CI], 0.91-1.00) and 0.57 (95% CI, 0.41-0.72), respectively. At a prevalence of 35%, the NPV of a PLASMIC score ≥5 was 0.99 (95% CI, 0.92-1.00). A PLASMIC score ≥6 was associated with a sensitivity and specificity of 0.85 (95% CI, 0.67-0.94) and 0.89 (95% CI, 0.81-0.94), respectively. The NPV of a PLASMIC score ≥6 at a prevalence of 35% was 0.92 (95% CI, 0.82-0.97).

CONCLUSION

A PLASMIC score threshold of ≥5 is associated with high sensitivity and NPV and may be a useful screening tool for identifying patients who are unlikely to have TTP and do not require TPE, though prospective assessment is required. A PLASMIC score <6 appears to have insufficient sensitivity to rule out TTP and the need for TPE.

MED-TMA: A clinical decision support tool for differential diagnosis of TMA with enhanced accuracy using an ensemble method

Considering difficulties in on-site ADAMTS13 testing and the performance instability of PLASMIC score according to ethnicity, we developed a prediction tool, MED-TMA (machine learning (ML) method for differential diagnosis (DDx) of thrombotic microangiopathy (TMA)) to support clinical decision. Data from 319 patients visiting 31 hospitals in Korea clinically diagnosed with primary TMA was randomly separated by 2:1 into two groups - the development dataset (D-set, n = 212), the validation dataset (V-set, n = 107). Feature elimination was conducted to select optimal clinical predictors. We developed the model with the selected features using ML methods, verifying using V-set. After the feature elimination using 19 clinical variables, five variables were selected with high importance value. Among nine ML methods, four ML methods were chosen considering the Area Under the Curves (AUC) and the correlation between the methods using D-set. We developed MED-TMA based on an optimized ensemble model with the selected four ML methods resulting in AUC values of 0.945 and 0.924 in D-set and V-set, respectively. In addition to the binary outcome, MED-TMA was capable of providing a probability for DDx of TMA. The ensemble approach driven MED-TMA showed comparable accurate and intuitive decision support for DDx of TMA to that of the existing models based on a single ML method. We provide a web-based nomogram for the appropriate use of effective but costly therapeutics to treat TMA patients (http://hematology.snu.ac.kr/medtma/).

Validation of PLASMIC score: an academic medical center case series (2012-present)

BACKGROUND

The PLASMIC score is a rapid and inexpensive tool for predicting severe ADAMTS13 deficiency (activity <10%) in patients with suspected thrombotic thrombocytopenic purpura (TTP) by analyzing seven parameters (platelet count; combined hemolysis variable; absence of active neoplasia; absence of an organ or stem-cell transplant; mean corpuscular value; international normalized ratio; and serum creatinine). The purpose of this study was to validate the PLASMIC score at a large multi-institutional academic medical center.

METHODS

An internal database of consultations to the transfusion medicine service, which oversees therapeutic apheresis at our institution, was reviewed to identify patients who were evaluated for and/or received plasma exchange for suspected TTP. These consultations covered the time period of January 2012 to February 2019. PLASMIC scoring criteria and ADAMTS13 assay results were abstracted from the electronic medical record, the PLASMIC score was calculated, and cases stratified into risk categories (low, intermediate, high risk) based on the score value.

RESULTS

Of 58 patients identified, 46 met inclusion criteria, and 27 demonstrated ADAMTS13 activity <10%. Correlation of severe ADAMTS13 deficiency with risk-stratified groups resulted in 78% sensitivity, 63% specificity, 75% positive predictive value (PPV), and 67% negative predictive value (NPV).

DISCUSSION

These findings paralleled those from validation studies performed at other institutions. They provided insufficient evidence to recommend routine use of the PLASMIC score to rule out TTP among patients at our hospitals. Nonetheless, these results reinforce the importance of early ADAMTS13 testing as a diagnostic triage tool for patients with suspected TTP.

Expert statement on the ICU management of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is fatal in 90% of patients if left untreated and must be diagnosed early to optimize patient outcomes. However, the very low incidence of TTP is an obstacle to the development of evidence-based clinical practice recommendations, and the very wide variability in survival rates across centers may be partly ascribable to differences in management strategies due to insufficient guidance. We therefore developed an expert statement to provide trustworthy guidance about the management of critically ill patients with TTP. As strong evidence was difficult to find in the literature, consensus building among experts could not be reported for most of the items. This expert statement is timely given the recent advances in the treatment of TTP, such as the use of rituximab and of the recently licensed drug caplacizumab, whose benefits will be maximized if the other components of the management strategy follow a standardized pattern. Finally, unanswered questions are identified as topics of future research on TTP.