Results of full blood count test may help ID rare bleeding disorder
Researchers say commonly used CBC can support diagnosis of ITP
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The results of a full blood count test — called a CBC, or complete blood count, by clinicians — may help distinguish people with thrombotic thrombocytopenic purpura (TTP) from healthy individuals, a study suggests.
Specifically, two parameters calculated from such testing, which measures the number and size of various cells in the blood, showed markedly different levels among individuals with and without the rare bleeding disorder, according to the researchers, who analyzed CBC results from more than 200 people. Half of the study’s participants had been diagnosed with TTP, while the other half were healthy individuals.
Compared with the healthy participants, those with TTP had a higher neutrophil-to-lymphocyte ratio (NLR) and hemoglobin-to-platelet ratio (HPR). Neutrophils and lymphocytes are immune white blood cells, while hemoglobin is the oxygen-carrying protein in red blood cells; platelets are tiny cell fragments key to blood clotting.
Conversely, individuals with TTP had a lower platelet-to-lymphocyte ratio (PLR), though this result did not distinguish the two groups as well as NLR and HPR, which showed a particularly strong ability to do so, the researchers noted.
Given that a full blood count is a routine test done by doctors, the scientists concluded that “these readily available CBC-derived indices may serve as [additional] laboratory markers to support the clinical diagnosis of TTP.”
The study, “Diagnostic Value of Hematological Inflammatory Indices (NLR, PLR, HPR) in Thrombotic Thrombocytopenic Purpura: A Case-Control Study,” was published in the journal Clinical and Applied Thrombosis/Hemostasis.
In TTP, small clots form in tiny blood vessels, restricting blood flow to organs and causing a wide range of symptoms. In the disease’s most common form, known as immune-mediated TTP, the immune system produces antibodies against ADAMTS13, an enzyme that normally helps prevent excessive clot formation.
Because TTP involves inflammation and platelet clumping in small blood clots, scientists have become interested in whether simple measures derived from a CBC count could provide additional information about the disease.
Investigating 3 key parameters of a full blood count test
Now, a team of researchers from Iran aimed to determine whether NLR, PLR, and HPR differed between people with TTP and healthy individuals. The researchers also wanted to know if these three measures were tied to clinical symptoms and length of hospitalization among patients.
Their study involved 114 people with TTP and 115 healthy individuals, who served as controls. All were followed at a hospital in Mashhad from 2010 through 2022. Blood cell counts and inflammatory measures were obtained from medical records at diagnosis and after treatment.
At diagnosis, the individuals with TTP had significantly higher white blood cell and neutrophil counts than controls, while platelet and lymphocyte counts were lower. Red blood cell counts and hemoglobin also were reduced, whereas established measures of inflammation, including C-reactive protein and erythrocyte sedimentation rate, were higher.
The three blood-cell ratios also differed significantly between groups. Mean NLR was 6.57 in people with TTP versus 1.59 in controls, while HPR was 3.84 compared with 0.58. In contrast, PLR was lower in the TTP patients, averaging 63.77 compared with 98.81 in controls.
The researchers then assessed how well each measure distinguished patients from controls using the area under the curve (AUC) measure. The maximum AUC value is 1, which represents perfect separation between two groups.
NLR performed best, with an AUC of 0.925, followed by HPR at 0.906 and PLR at 0.791.
A test’s sensitivity is its ability to correctly identify those with a given disease, while specificity refers to correctly identifying those without it. Results showed that an NLR value higher than 1.96 identified TTP with 91.2% sensitivity and 100% specificity. An HPR value higher than 0.85 had 79.8% sensitivity and 98.3% specificity, while a PLR of 68.20 or lower had 69.3% sensitivity and 94.8% specificity.
However, the researchers noted the need for “external validation in independent [groups] before these thresholds can be recommended for routine clinical application.”
Further research needed on use of CBC test in routine practice
At hospital admission, fatigue, fever, abdominal pain, headache, jaundice, and vomiting were reported in 70% of those with ITP. Kidney-related symptoms were present in 41% of the ITP patients, while 40% had bleeding symptoms and 23% had neurological manifestations.
The blood ratios also showed associations with some clinical features. NLR was tied to kidney involvement, while PLR and HPR were linked with certain bodywide symptoms and thrombocytopenia, or low platelet counts. Bleeding was associated with a longer hospital stay, the data showed. The average hospitalization was 28.5 days.
[Test results from a full blood count could have] diagnostic value alongside established clinical criteria.
The researchers also explored associations between treatments, blood measures, and hospitalization. However, because treatment was not randomly assigned, the team cautioned that those results could reflect disease severity and clinician preference rather than an actual cause.
Among the study’s limitations were its retrospective design, meaning it looked backward in time at preexisting data, and its use of data from a single center. Additionally, the researchers noted that ADAMTS13 activity, which is used to confirm TTP, was unavailable for most patients.
Before using the results of a full blood count in diagnosing patients, “confirmation in larger, prospective studies will be important to define their place in routine practice,” the team noted.
Still, the findings overall suggest that NLR, PLR, and HPR could have “diagnostic value alongside established clinical criteria,” for diagnosing TTP, the researchers wrote.
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