Masked thrombocytopenia in a child with thalassemia and dengue : the pitfalls of automated platelet counting
Nivetha R, Rakshana R, Suresh Kannan K, Kumaravel K S
Department of Pediatrics, Govt. Mohan Kumaramangalam Medical College, Salem, India
Address for Correspondence: Nivetha Rajan, Department of Pediatrics, Government Mohan Kumaramangalam Medical College Hospital, Salem, Maharashtra - 636001
Email: nivirajan4520@gmail.com
Keywords: Complete blood count, Dengue, Fragmented RBC
Clinical Problem :
A 10-year-old boy, who is a known case of beta thalassemia intermedia, was admitted with complaints of fever for four days, persistent vomiting for two days, a few episodes of loose stools, and abdominal pain. On examination, the boy was febrile and had shock and hepatosplenomegaly. He had typical features of dengue, including pleural effusion, gall bladder wall edema, shock, and ascites. However, the automated CBC performed by Sysmax XP100 showed a normal platelet count. In view of the strong clinical suspicion, a manual platelet count was performed, which revealed thrombocytopenia. Peripheral smear evaluation showed microcytic hypochromic red blood cells with marked anisopoikilocytosis. Numerous abnormal red cell forms were noted, including fragmented red blood cells, microspherocytes, target cells, elongated cells, and teardrop cells. Nucleated red blood cells and polychromasia were also observed. Platelets appeared reduced in number on smear examination. Serum Anti-Dengue IgM Antibody was positive on day 7 of fever. Subsequent automated CBC continued to show a normal platelet count, whereas repeated manual platelet counts consistently demonstrated thrombocytopenia (Table 1).
Table 1. Serial hematological parameters.
| Days of fever |
WBC count (x103/µL) |
RBC count (x106/µL) |
Hemoglobin (g/dl) |
Hematocrit (%) |
Platelet Count (x103/µl) |
Manual platelet count (x103/µl) |
| 5 |
5.3 |
3.37 |
7.4 |
23.8 |
364 |
84 |
| 6 |
3.3 |
2.88 |
6.4 |
20.5 |
385 |
77 |
| 11 |
5.4 |
3.35 |
8 |
24.9 |
270 |
85 |
| 12 |
4.8 |
3.35 |
8 |
24.9 |
300 |
90 |
|
What are the different methods of counting platelets and their significance?
Discussion :
The complete blood count (CBC) forms the foundation for pediatric hematological evaluation. Accurate platelet estimation is crucial in children, as thrombocytopenia may be the earliest or only indicator of serious underlying pathology. The platelet count in a CBC can be performed using various manual and automated techniques, each based on different principles to ensure accurate and reliable estimation Table 2. 1 Peripheral smear examination remains an essential component of hematological evaluation, especially when automated results are inconsistent with clinical findings. Manual platelet counting provides a more accurate estimation in such situations and helps prevent misinterpretation of laboratory data. Despite the accuracy and reliability of automated hematology analyzers, certain clinical conditions associated with significant red blood cell morphological abnormalities may interfere with platelet estimation. 2,3 Small red blood cell fragments and microerythrocytes may be misclassified as platelets due to size-based detection principles. This leads to falsely normal platelet counts. In the present case, the presence of fragmented red blood cells and marked red cell morphological abnormalities contributed to erroneous platelet estimation by the automated analyzer that utilized impedence method for platelet counting. In patients with significant red cell abnormalities, automated platelet counts may be misleading. 4,5 Manual platelet estimation should be performed whenever platelet counts are markedly abnormal or inconsistent with clinical assessment. This case highlights the importance of correlating automated CBC results with peripheral smear findings. Dengue management decisions must not rely solely on automated CBC. Careful laboratory-clinical correlation is essential for accurate diagnosis and appropriate patient management.
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- Shetty A, Gaffoor N. Spurious thrombocytosis in beta thalassemia intermedia - even auto analyzers do get perplexed! Journal of Applied Hematology. 2023;14(3):255-256.
- Krishnamurthy V, Shivamurthy A, Kumar PV. Platelet count in impedance-based hematology analyzer: beware of trap! Asian Journal of Transfusion Science. 2023;17(1):131-132.
- ChaicharoenTantanate, Khowawisetsut L, Pattanapanyasat K. Performance evaluation of automated impedance and optical fluorescence platelet counts compared with international reference method in patients with thalassemia. Arch Pathol Lab Med. 2017;141(6):830-836.
- Wituska M, Ciepiela O. Application of hybrid platelet technology for platelet count improves accuracy of PLT measurement in samples from patients with different types of anemia. J Clin Med. 2025;14(15):5401.
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