Delayed diagnosis of fetal and neonatal alloimmune thrombocytopenia: a cause of perinatal mortality and morbidity

Accuracy of Umbilical Cord Complete Blood Count in Detecting Early-Onset Neonatal Thrombocytopenia

BACKGROUND

Neonatal thrombocytopenia (NTCP) is a common hematological disorder whose platelet count falls below the normal limit of 150 x 109/L. NTCP can cause late complications if left untreated. The current study aimed to evaluate the accuracy of the umbilical cord complete blood count (UC CBC) in detecting early-onset neonatal thrombocytopenia (EO-NTCP). Further, the prevalence of NTCP was also investigated.  Methods: A cross-sectional study with a matched control was conducted on all newborns delivered at a tertiary care center in Jeddah, Saudi Arabia, between May 2016 and 2019. After exclusions, 40 neonates with EO-NTCP (cases) and 80 without EO-NTCP (controls) were included. The case-to-control ratio was 1:2. The results of UC CBC were compared with those of follow-up CBC, performed within 72 hours. A p-value of <0.05 was considered statistically significant. All data were analyzed using IBM SPSS version 28 for Windows (IBM Corp., Armonk, NY).

RESULTS

The prevalence of NTCP was approximately 1.02% (111/10,936). Lack of antenatal care was found in 12 (30%) neonates with EO-NTCP vs. 10 (12.5%) neonates without EO-NTCP (p = 0.02). Neonates with EO-NTCP were more likely to have experienced intrauterine growth restriction (5 (37.5%) vs. 5 (6.3%), p < 0.001) and oligohydramnios (5 (12.5%) vs. 0 (0%), p = 0.003). Neonates who developed EO-NTCP were more likely to be admitted to the NICU (34 (85%) vs. 35 (43.8%), p < 0.001) and receive antibiotics (22 (55%) vs. 25 (31.3%), p = 0.012). Also, neonates with EO-NTCP were more frequently diagnosed with neonatal sepsis (7 (17.5%) vs. 3 (3.8%), p = 0.015) and more likely to receive platelet transfusions (15 (37.5% vs. 1 (1.3%), p < 0.001). They also had a higher median length of hospital stay (13 (interquartile range (IQR) 3-28) vs. 4 (IQR 2-9) days, p = 0.006). The mortality rates of neonates with EO-NTCP and those without were 6 (15%) vs. 2 (2.5%) neonates (p = 0.016). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of UC CBC were 62.50%, 97.50%, 20.40%, and 99.61%, respectively.

CONCLUSION

The prevalence of EO-NTCP in King Abdulaziz Medical City is comparable to international and national figures, and it is associated with preceding maternal comorbidities, serious neonatal morbidity, and even mortality. Therefore, proper antenatal care is vital in preventing maternal and neonatal morbidities, including the risks of NTCP and its related complications. With high NPV, using UC CBC as a universal screening method could assist in safely discharging newborns. However, because of its low sensitivity, a comprehensive clinical examination with confirmatory laboratory tests are still the cornerstone in diagnosing EO-NTCP. Future trials should aim to study the cost-effectiveness of universal UC CBC and the long-term outcomes of infants diagnosed with EO-NTCP.

Cellular surface plasmon resonance-based detection of anti-HPA-1a antibody glycosylation in fetal and neonatal alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease manifests itself in only a fraction of pregnancies, most commonly with anti-HPA-1a antibodies. We found that in particular, the core fucosylation in the IgG-Fc tail is highly variable in anti-HPA-1a IgG, which strongly influences the binding to leukocyte IgG-Fc receptors IIIa/b (FcγRIIIa/b). Currently, gold-standard IgG-glycoanalytics rely on complicated methods (e.g., mass spectrometry (MS)) that are not suited for diagnostic purposes. Our aim was to provide a simplified method to quantify the biological activity of IgG antibodies targeting cells. We developed a cellular surface plasmon resonance imaging (cSPRi) technique based on FcγRIII-binding to IgG-opsonized cells and compared the results with MS. The strength of platelet binding to FcγR was monitored under flow using both WT FcγRIIIa (sensitive to Fc glycosylation status) and mutant FcγRIIIa-N162A (insensitive to Fc glycosylation status). The quality of the anti-HPA-1a glycosylation was monitored as the ratio of binding signals from the WT versus FcγRIIIa-N162A, using glycoengineered recombinant anti-platelet HPA-1a as a standard. The method was validated with 143 plasma samples with anti-HPA-1a antibodies analyzed by MS with known clinical outcomes and tested for validation of the method. The ratio of patient signal from the WT versus FcγRIIIa-N162A correlated with the fucosylation of the HPA-1a antibodies measured by MS (r=-0.52). Significantly, FNAIT disease severity based on Buchanan bleeding score was similarly discriminated against by MS and cSPRi. In conclusion, the use of IgG receptors, in this case, FcγRIIIa, on SPR chips can yield quantitative and qualitative information on platelet-bound anti-HPA-1a antibodies. Using opsonized cells in this manner circumvents the need for purification of specific antibodies and laborious MS analysis to obtain qualitative antibody traits such as IgG fucosylation, for which no clinical test is currently available.

DOWN'S SYNDROME WITH NEONATAL ALLOIMMUNE THROMBOCYTOPENIA DUE TO HLA-A2 ANTIBODY

Anti-HLA antibodies reportedly exist in the one third of pregnant women. But few occurrences of neonatal alloimmune thrombocytopenia (NAIT) caused by anti-HLA antibodies have been reported. Here a male baby, who was admitted for low birth weight with Down syndrome (DS), was suffered from thrombocytopenia without transient myeloproliferative disorder (TMD). Positive reactions of HLA-specific antibodies were detected in maternal serum. Cross-matching tests between maternal serum and paternal platelets and lymphocytes were strongly positive. It is most conceivable that the previous pregnancy of the mother induced the production of anti-HLA-A2 antibody, which crossed the placenta and subsequently caused an NAIT in the case presented. This is the first case of DS with NAIT due to anti-HLA antibodies.

Incidence and consequences of neonatal alloimmune thrombocytopenia: a systematic review

BACKGROUND

Neonatal alloimmune thrombocytopenia (NAIT) is a potentially devastating disease that may lead to intracranial hemorrhage in the fetus or neonate, often with death or major neurologic damage. There are no routine screening programs for NAIT, preventive measures are taken only in a subsequent pregnancy. To estimate the population incidence of NAIT and its consequences, we conducted a review of the literature. Our results may aid in the design of a screening program.

METHODS

An electronic literature search included Medline, Embase, Cochrane database and references of retrieved articles. Eligible for inclusion were all prospective studies aimed at diagnosing NAIT in a general, nonselected newborn population, with sufficient information on platelet count at birth, bleeding complications, and treatment. Titles and abstracts were reviewed, followed by review of full text publications. Studies were independently assessed by 2 reviewers for methodologic quality. Disagreements were resolved by consensus, including a third reviewer.

RESULTS

From the initial 768 studies, 21 remained for full text analysis, 6 of which met the inclusion criteria. In total, 59,425 newborns were screened, with severe thrombocytopenia in 89 cases (0.15%). NAIT was diagnosed in 24 of these 89 newborns (27%). In 6 (25%) of these cases, an intracranial hemorrhage was found, all likely of antenatal origin.

CONCLUSIONS

NAIT is among the most important causes of neonatal thrombocytopenia. Intracranial hemorrhage due to NAIT occurs in 10 per 100 000 neonates, commonly before birth. Screening for NAIT might be effective but should be done antenatally.

Neonatal thrombocytopenia: etiology, management and outcome

Thrombocytopenia is a very common hematological abnormality found in newborns, especially in preterm neonates. Two subgroups can be distinguished: early thrombocytopenia, occurring within the first 72 hours of life, and late thrombocytopenia, occurring after the first 72 hours of life. Early thrombocytopenia is associated with intrauterine growth restriction, whereas late thrombocytopenia is caused mainly by sepsis and necrotizing enterocolitis (NEC). Platelet transfusions are the hallmark of the treatment of neonatal thrombocytopenia. Most of these transfusions are prophylactic, which means they are given in the absence of bleeding. However, the efficacy of these transfusions in preventing bleeding has never been proven. In addition, risks of platelet transfusion seem to be more pronounced in preterm neonates. Because of lack of data, platelet transfusion guidelines differ widely between countries. This review summarizes the current understanding of etiology and management of neonatal thrombocytopenia.