PLR (Platelet–Lymphocyte Ratio): Understanding Your Blood Test Series

1. Overview: What this test reveals and why it is important

The platelet–lymphocyte ratio (PLR) is a simple, inexpensive, and widely available inflammatory marker derived from the complete blood count with differential. It is calculated by dividing the absolute platelet count by the absolute lymphocyte count.

PLR reflects the interplay between two distinct haematopoietic lineages:

· Platelets are anucleate cell fragments derived from megakaryocytes. Beyond their canonical role in haemostasis and thrombosis, platelets are potent mediators of inflammation. They store and release chemokines, express adhesion molecules, interact with leukocytes, and promote endothelial activation. Thrombocytosis (elevated platelets) often accompanies chronic inflammation, malignancy, and iron deficiency.

· Lymphocytes are the architects of adaptive immunity. They include T cells, B cells, and natural killer cells. Lymphopenia signals physiological stress, immunosuppression, or exhaustion of the adaptive immune reservoir.

An elevated PLR indicates either thrombocytosis (increased platelet‑driven inflammation), lymphopenia (suppressed adaptive immunity), or both. This pattern is a hallmark of systemic inflammation, immune dysregulation, and adverse prognosis across multiple disease states. A low PLR generally reflects balanced inflammation and competent adaptive immunity.

Clinical utility: PLR is not a diagnostic test but a validated prognostic and risk‑stratification marker. It has been extensively studied in:

· Cardiovascular disease: PLR predicts major adverse cardiac events, mortality after myocardial infarction, and severity of heart failure and peripheral artery disease.

· Oncology: Pre‑treatment PLR independently predicts poorer survival in colorectal, lung, breast, gastric, pancreatic, ovarian, and hepatocellular carcinomas, as well as haematological malignancies.

· Infectious diseases: PLR correlates with severity in sepsis, COVID‑19, pneumonia, and tuberculosis.

· Autoimmune / inflammatory disorders: PLR reflects disease activity in rheumatoid arthritis, lupus, inflammatory bowel disease, and vasculitis.

· Chronic kidney disease: PLR predicts cardiovascular events and progression to end‑stage renal disease.

PLR is cheap, universally available, and can be trended serially. It must always be interpreted alongside the clinical context, absolute platelet and lymphocyte counts, and other inflammatory markers (CRP, ESR, NLR).

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2. What does it measure

a. Units of measurement

· Dimensionless ratio – calculated as:

· PLR = Absolute platelet count (×10⁹/L or /μL) ÷ Absolute lymphocyte count (×10⁹/L or /μL)

· Since both numerator and denominator share the same unit, the ratio is unit‑free.

b. Normal Range and Optimal Targets

(Reference intervals vary by age, sex, ethnicity, and laboratory; the following are derived from large population studies and prognostic cut‑points.)

Adults:

· Optimal / low risk: PLR less than 120

· Normal / acceptable: PLR 120–150

· Borderline elevated: PLR 150–200

· Elevated / adverse prognosis: PLR 200–300

· Severely elevated / high risk: PLR greater than 300

Children:

· Normal ranges are age‑dependent; infants have higher lymphocyte counts, resulting in lower PLR.

· Infants and toddlers: often 50–150

· Older children: progressively approach adult ranges by adolescence.

· Use age‑matched reference ranges from the reporting laboratory.

Elderly:

· Mild age‑related increase in PLR due to immunosenescence (lymphopenia) and increased inflammatory stimuli.

Interpretation notes:

· PLR is a continuous variable; there is no universal threshold. Different diseases and clinical contexts use different cut‑points.

· Isolated elevated PLR with normal absolute counts should prompt repeat testing; transient infection, stress, or dehydration may cause temporary elevation.

· Very low PLR (<50) is uncommon in adults and may indicate thrombocytopenia (bleeding risk) or lymphocytosis; investigate if persistent.

· Always examine the absolute platelet and lymphocyte counts – the ratio alone does not reveal which lineage is deranged.

· PLR is often used together with NLR (neutrophil–lymphocyte ratio) to provide complementary prognostic information.

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3. Other factors connected to this

a. Direct correlation (factors that directly raise PLR)

PLR is increased by thrombocytosis, lymphopenia, or both.

Factors that cause thrombocytosis (↑ platelets, ↑ PLR):

· Reactive (secondary) thrombocytosis:

· Acute inflammation / infection: bacterial infections, abscess, pneumonia, osteomyelitis.

· Chronic inflammation: rheumatoid arthritis, inflammatory bowel disease, vasculitis, sarcoidosis.

· Tissue injury / necrosis: surgery, trauma, burns, pancreatitis, myocardial infarction.

· Malignancy: solid tumours (paraneoplastic), lymphoma.

· Iron deficiency anaemia – a common and often unrecognised cause.

· Haemorrhage / haemolysis: acute blood loss, haemolytic anaemia.

· Post‑splenectomy – loss of platelet sequestration.

· Rebound phenomenon: after chemotherapy or alcohol withdrawal.

· Medications: corticosteroids, vincristine, epinephrine.

· Essential (primary) thrombocytosis:

· Essential thrombocythaemia (ET) – myeloproliferative neoplasm, often with JAK2 mutation.

· Polycythaemia vera, chronic myeloid leukaemia – may present with thrombocytosis.

Factors that cause lymphopenia (↓ lymphocytes, ↑ PLR):

· Acute stress / critical illness: trauma, surgery, myocardial infarction, sepsis – cortisol‑mediated.

· Infections: viral (HIV, influenza, COVID‑19, hepatitis), bacterial sepsis, tuberculosis.

· Immunosuppressive therapy: corticosteroids, chemotherapy, radiation, calcineurin inhibitors, mycophenolate.

· Autoimmune diseases: SLE, rheumatoid arthritis, sarcoidosis.

· Malnutrition / protein‑energy wasting: alcoholism, anorexia nervosa.

· Genetic: DiGeorge syndrome, severe combined immunodeficiency (SCID).

· Haematological: aplastic anaemia, advanced lymphoma, leukaemia.

· Ageing: physiological decline in T‑cell production.

Thus, elevated PLR is associated with:

· Chronic inflammation and autoimmune disease.

· Malignancy.

· Iron deficiency.

· Post‑splenectomy state.

· Myeloproliferative neoplasms.

· Physiological stress and immunosuppression.

· Poor nutritional status.

b. Indirect correlation (factors that influence PLR interpretation or cause artefactual changes)

· Circadian rhythm: platelet and lymphocyte counts exhibit diurnal variation. For serial comparisons, collect blood at a consistent time.

· Exercise: intense acute exercise causes transient thrombocytosis and lymphocytosis, followed by delayed lymphopenia. Defer testing after strenuous exertion.

· Pregnancy: platelets may fall slightly; lymphocytes decline; PLR may increase. Not a reliable marker during pregnancy.

· Smoking: chronic smokers have elevated platelets and may have lower lymphocytes; PLR is often chronically elevated.

· Alcohol: chronic alcoholism causes thrombocytopenia (lowers PLR) and lymphopenia (raises PLR) – net effect variable.

· Medications:

· Increase PLR: corticosteroids, vincristine, epinephrine (thrombocytosis); immunosuppressants (lymphopenia).

· Decrease PLR: chemotherapy (thrombocytopenia, lymphopenia – effect on ratio unpredictable), antiplatelet agents (no direct effect on platelet count).

· Iron deficiency: causes reactive thrombocytosis; PLR elevated; correct iron, PLR normalises.

· Splenectomy: thrombocytosis without lymphopenia → PLR increases markedly.

· Assay variability: automated haematology analysers may misclassify platelet clumps (pseudothrombocytopenia) or giant platelets; manual review if abnormal.

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4. Disorders related to abnormal values

a. When PLR is elevated (clinically significant – adverse prognostic marker)

Cardiovascular disease:

· Acute coronary syndrome / myocardial infarction: Elevated PLR at presentation independently predicts in‑hospital mortality, heart failure, and long‑term major adverse cardiac events.

· Ischaemic stroke: PLR correlates with infarct volume, haemorrhagic transformation, and poor functional outcome.

· Heart failure: PLR predicts hospitalisation and cardiovascular death.

· Peripheral arterial disease: PLR associates with disease severity and amputation risk.

Oncology:

· Solid tumours: Pre‑treatment PLR >150–200 (varies by tumour type) predicts poorer overall and progression‑free survival in colorectal, lung, breast, gastric, pancreatic, ovarian, hepatocellular, and renal cell carcinoma. PLR is incorporated into prognostic scores (e.g., in colorectal cancer liver metastases).

· Haematological malignancies: Elevated PLR at diagnosis correlates with aggressive disease in lymphoma, multiple myeloma, and acute leukaemia.

· Surgical oncology: Preoperative PLR predicts postoperative complications and recurrence.

Infectious diseases:

· Sepsis / bacteraemia: PLR >200–250 strongly suggests bacterial infection and predicts progression to septic shock and death.

· COVID‑19: PLR >180–200 at admission identifies patients at high risk of severe disease, intensive care admission, and mortality.

· Tuberculosis: PLR correlates with disease extent and cavitation.

· HIV: PLR reflects immune activation and disease progression.

Autoimmune / inflammatory diseases:

· Rheumatoid arthritis, SLE, inflammatory bowel disease: PLR reflects disease activity; normalises with successful immunosuppression.

· Vasculitis: Elevated PLR at diagnosis predicts relapses.

· Sarcoidosis: PLR associates with progressive pulmonary disease.

Chronic kidney disease:

· PLR predicts cardiovascular events, progression to end‑stage renal disease, and all‑cause mortality.

Iron deficiency anaemia:

· Reactive thrombocytosis elevates PLR; PLR normalises with iron repletion.

Essential thrombocythaemia (ET):

· Markedly elevated PLR due to extreme thrombocytosis; PLR reflects disease burden and thrombotic risk.

b. When PLR is low (usually favourable, but context‑dependent)

· Generally desirable: low PLR indicates balanced platelet and lymphocyte counts, low inflammatory activity.

· Physiological: children, healthy adults with regular exercise, non‑smokers.

· Lymphocytosis: infections (EBV, pertussis, CMV), chronic lymphocytic leukaemia – PLR may be very low, but this is not protective if due to malignancy.

· Thrombocytopenia: immune thrombocytopenia (ITP), chemotherapy, liver disease, bone marrow failure – PLR may be low, but this confers bleeding risk.

· Recovery phase: after bone marrow transplant or chemotherapy, lymphocyte recovery may precede platelet recovery, transiently lowering PLR.

Interpretation note: An isolated low PLR in an otherwise healthy, asymptomatic individual with normal absolute counts is not a cause for concern and does not require investigation.

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5. Best way to address aberrant levels

Important principle: PLR is a marker, not a disease. There is no treatment to directly normalise PLR. Intervention must target the underlying condition causing thrombocytosis or lymphopenia. Normalising PLR is a sign that the underlying disease is controlled, inflammation is subsiding, nutritional status is improving, or the offending medication has been adjusted.

a. Quick ways or using Medications

There is no medication approved specifically to lower PLR. The following interventions address the underlying causes:

For thrombocytosis:

· Reactive thrombocytosis:

· Iron deficiency anaemia: oral or intravenous iron replacement – platelets normalise within 4–8 weeks.

· Infection / inflammation: treat underlying condition; platelets normalise with resolution.

· Post‑splenectomy: no treatment required; thrombocytosis is benign and antiplatelet therapy is not routinely indicated unless very high risk.

· Essential thrombocythaemia (ET):

· Low‑dose aspirin – reduces thrombotic risk.

· Cytoreductive therapy: hydroxyurea, anagrelide, or interferon‑α for high‑risk patients (age >60, prior thrombosis, platelets >1500×10⁹/L).

· JAK2 inhibitor: ruxolitinib in resistant/intolerant cases.

For lymphopenia:

· Treat underlying infection: antiretroviral therapy for HIV, antiviral agents.

· Reduce immunosuppression: taper corticosteroids when possible, switch to less lymphotoxic agents.

· Nutritional repletion: correct deficiencies of protein, zinc, vitamin B12, folate.

· Treat autoimmune disease: immunosuppressive therapy may cause lymphopenia; balance disease control against lymphocyte preservation.

For acute stress / critical illness:

· Haemodynamic stabilisation: fluids, vasopressors, source control.

· Supportive care: adequate oxygenation, nutrition, glycaemic control.

Do not self‑prescribe – all prescription medications require medical supervision.

b. Using Supplements or Holistic medicine

Supplements with evidence for supporting platelet–lymphocyte balance – as adjuncts to definitive therapy:

For reducing reactive thrombocytosis and platelet activation:

· Omega‑3 fatty acids (EPA/DHA):

· Reduce platelet aggregation and activation; may modestly lower platelet counts in reactive thrombocytosis.

· Preferred source: Algae oil – sustainable, plant‑based, direct EPA/DHA, no marine contaminants.

· Avoid conventional fish oil (overfishing, ocean pollution, ethical concerns).

· Dose: 2–4 g/day EPA/DHA for anti‑inflammatory and antiplatelet effect.

· Iron (for iron deficiency anaemia):

· Correcting iron deficiency normalises reactive thrombocytosis and lowers PLR.

· Preferred form for tolerability: ferrous bisglycinate – chelated, fewer gastrointestinal side effects.

· Plant‑based / fermentation‑derived: iron bisglycinate; heme iron analogues from precision fermentation are emerging.

· Do not take iron unless deficiency is confirmed – iron overload is harmful.

· Curcumin (turmeric):

· Anti‑inflammatory; inhibits platelet activation and megakaryocyte proliferation.

· Use phytosomal, liposomal, or with piperine for bioavailability.

· Avoid products with added synthetic folic acid or cyanocobalamin.

· Green tea catechins (EGCG):

· Anti‑inflammatory, anti‑thrombotic; may suppress megakaryocyte development.

· Use beverage (2–3 cups/day) rather than concentrated extracts (hepatotoxicity risk).

· Garlic (Allium sativum):

· Aged garlic extract; modest antiplatelet effect; minimal effect on platelet count.

For supporting lymphocyte recovery and reducing lymphopenia:

· Vitamin D:

· Deficiency is associated with lymphopenia and immune dysregulation.

· Supplementation improves lymphocyte proliferation and function.

· Preferred: D3 (cholecalciferol) from lichen.

· Dose: 600–2000 IU/day for maintenance; higher doses for deficiency correction (under guidance).

· Zinc:

· Essential for T‑cell development and function; deficiency causes lymphopenia.

· Supplementation in deficient individuals increases lymphocyte counts and improves PLR.

· Preferred form: zinc picolinate or zinc citrate.

· Dose: 15–30 mg elemental zinc/day; monitor copper with long‑term use.

· Vitamin B12 and folate:

· Deficiency causes ineffective haematopoiesis, including lymphopenia.

· Use methylcobalamin and methylfolate – active forms, avoid synthetic folic acid and cyanocobalamin.

· Dose: methylcobalamin 1000–2000 mcg/day, methylfolate 400–1000 mcg/day if deficient.

· Vitamin C:

· Supports immune cell function; may reduce oxidative stress.

· High‑dose intravenous vitamin C used experimentally in sepsis; oral supplementation for PLR improvement lacks robust evidence.

· Selenium:

· Co‑factor for antioxidant enzymes; deficiency impairs lymphocyte proliferation.

· Supplementation in deficient individuals may improve immune function.

· Ashwagandha (Withania somnifera):

· Adaptogen; may reduce stress‑induced lymphopenia.

· Limited evidence; use standardised extracts from GMP‑certified manufacturers.

· Reishi mushroom (Ganoderma lucidum):

· Beta‑glucans; immunomodulatory, may enhance lymphocyte activity.

· Preferred source: fruiting body extract, certified organic.

Supplements to avoid:

· Products with added synthetic folic acid or cyanocobalamin – use methylfolate and methylcobalamin if needed.

· Unregulated herbal blends with undisclosed ingredients.

· High‑dose vitamin E – may impair platelet function and immune response.

c. Using Diet and Foods (following a plant‑forward, ecologically sustainable approach)

Diet is a cornerstone of inflammation control, platelet health, and immune competence. A well‑designed, nutrient‑dense plant‑based diet supports lymphocyte function, modulates platelet activity, and promotes a favourable PLR.

Core dietary principles – what to emphasise:

· Anti‑inflammatory dietary pattern:

· Mediterranean‑style plant‑forward diet – abundant vegetables, fruits, legumes, whole grains, nuts, seeds, olive oil.

· High in polyphenols, fibre, unsaturated fats, and antioxidants.

· Low in refined carbohydrates, added sugars, and saturated fats.

· Consistently associated with lower inflammatory markers and reduced platelet activation.

· Adequate protein intake:

· Essential for lymphocyte synthesis and immune competence.

· Plant‑based protein sources (hierarchy adhered):

· Primary: legumes (lentils, chickpeas, beans, soy products – tofu, tempeh, edamame).

· Fungi / algae: mycoprotein (Quorn), spirulina, chlorella.

· Biotechnology: precision‑fermented dairy proteins (animal‑free whey, casein) – acceptable emerging options.

· Dairy / eggs: permitted but not emphasised; low‑fat fermented dairy (yoghurt, kefir) if tolerated.

· Meat, poultry, fish: deliberately omitted. Effective plant‑based alternatives exist to meet all protein requirements for immune health.

· Iron‑rich plant foods (for iron deficiency):

· Lentils, chickpeas, tofu, pumpkin seeds, quinoa, fortified cereals, dark leafy greens (cooked spinach, kale).

· Enhance absorption with vitamin C (citrus, bell peppers, amla); avoid tea/coffee with meals.

· Zinc‑rich plant foods:

· Pumpkin seeds, hemp seeds, chickpeas, lentils, cashews, quinoa.

· Soaking and sprouting legumes and seeds reduces phytate and enhances zinc absorption.

· Vitamin B12:

· No reliable plant‑based whole food source. Must be supplemented or obtained from fortified foods (plant milks, nutritional yeast with methylcobalamin).

· Precision‑fermented B12 – ecologically responsible, non‑animal, preferred.

· Folate:

· Abundant in leafy greens, legumes, asparagus, beets, sunflower seeds.

· Deficiency impairs lymphocyte proliferation.

· Vitamin C‑rich foods:

· Citrus fruits, guava, bell peppers, broccoli, kiwi, strawberries, amla (Indian gooseberry).

· Vitamin D:

· Sunlight exposure primary; fortified plant milks; supplement from lichen if needed.

· Selenium:

· Brazil nuts (1–2 per day), sunflower seeds, mushrooms, whole grains.

· Omega‑3 fatty acids:

· ALA sources: ground flaxseeds, chia seeds, hemp seeds, walnuts.

· Direct EPA/DHA: microalgae (spirulina, chlorella – limited amounts); algae oil supplements for therapeutic doses.

· Polyphenol‑rich foods:

· Berries, green tea, dark chocolate (≥70% cocoa), extra virgin olive oil, turmeric, ginger, cruciferous vegetables.

· Fermented plant foods:

· Kimchi, sauerkraut, kombucha, miso, tempeh – support gut microbiome diversity and reduce systemic inflammation.

· Mushrooms:

· Shiitake, maitake, oyster, reishi – beta‑glucans and ergothioneine; immunomodulatory.

What to avoid or severely limit:

· Ultra‑processed foods, refined carbohydrates, added sugars – promote inflammation and impair immune function.

· Excess alcohol – causes thrombocytopenia (variable) and lymphopenia; abstinence recommended if PLR is elevated due to lymphopenia.

· Trans fats – partially hydrogenated oils.

· Saturated fats – excess intake may promote platelet activation and inflammation.

· Red and processed meats – associated with systemic inflammation and iron overload (in hereditary haemochromatosis); not required.

· Smoking – single most important modifiable risk factor for elevated PLR (increases platelets, reduces lymphocytes); cessation improves both counts.

Lifestyle factors with proven benefit for PLR:

· Regular moderate aerobic exercise: 30–60 minutes, most days – reduces resting platelet reactivity, enhances lymphocyte circulation, and lowers PLR.

· Stress reduction: chronic stress elevates cortisol, causing lymphopenia and possibly thrombocytosis; mindfulness, meditation, yoga, adequate sleep.

· Smoking cessation: PLR decreases within weeks to months of quitting.

· Weight loss: in overweight/obese individuals, 5–10% weight loss reduces systemic inflammation and improves PLR.

· Sleep hygiene: 7–9 hours of quality sleep per night supports adaptive immunity and normal platelet function.

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6. How soon can one expect improvement and the ideal time frame to retest

PLR is moderately dynamic; response time depends on the underlying cause.

For reactive thrombocytosis (iron deficiency, infection, inflammation):

· Iron replacement: platelets begin to fall within 1–2 weeks; normalisation in 4–8 weeks.

· Infection / inflammation resolution: platelets normalise within 2–4 weeks after resolution.

· Repeat testing: at 4–8 weeks after intervention.

For essential thrombocythaemia on cytoreductive therapy:

· Hydroxyurea / anagrelide: platelet reduction detectable in 2–4 weeks; maximal effect at 6–12 weeks.

· Repeat testing: every 4–8 weeks during dose titration; every 3–6 months when stable.

For lymphopenia:

· Nutritional repletion (zinc, B12, folate, vitamin D): lymphocyte counts increase within 2–4 weeks; PLR improves over 4–8 weeks.

· Reduction of immunosuppression: lymphocyte recovery over 4–12 weeks.

· HIV antiretroviral therapy: CD4 recovery is slow; PLR improves over 3–6 months.

· Repeat testing: at 2–3 months for nutritional intervention; at 3–6 months for HIV/immunosuppression.

For lifestyle interventions:

· Smoking cessation: PLR begins to decrease within 2–4 weeks; maximal effect at 3–6 months.

· Weight loss / exercise: PLR improvement detectable in 3–6 months with sustained lifestyle change.

· Alcohol abstinence: PLR normalises over 4–8 weeks.

Retesting interval summary:

· Reactive thrombocytosis: repeat at 4–8 weeks after correcting underlying cause.

· Essential thrombocythaemia: as directed by haematologist; typically every 3–6 months.

· Lymphopenia due to nutritional deficiency: repeat at 2–3 months.

· Chronic inflammatory / autoimmune disease on treatment: every 3–6 months.

· Lifestyle modification: repeat at 3–6 months.

· Routine health screen: every 1–2 years in stable, healthy individuals.

Do not retest PLR more often than every 4 weeks in chronic stable conditions; in acute illness, serial monitoring may be warranted every 48–72 hours until trending downward.

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Conclusion

The platelet–lymphocyte ratio is a composite window into two ancient defence systems: the megakaryocyte‑derived platelet, first responder to vascular injury and now recognised as a sentinel of inflammation; and the lymphocyte, custodian of immunological memory and adaptive precision. An elevated PLR signals that these systems are out of balance – platelets are overproduced, lymphocytes are depleted, or both.

This ratio does not diagnose; it prognosticates. It stratifies risk in myocardial infarction, predicts outcomes in cancer, reflects disease activity in autoimmunity, and alerts the clinician to occult iron deficiency. A falling PLR is a sign of therapeutic success; a persistently elevated PLR demands investigation and intervention.

There is no pill to lower PLR. The ratio normalises only when the root cause is addressed – iron stores replenished, infection cleared, inflammation quelled, myeloproliferation controlled, nutritional status restored.

A plant‑based, ecologically responsible diet – rich in legumes, whole grains, nuts, seeds, mushrooms, and algae‑derived omega‑3s – provides the nutrients essential for lymphocyte health (zinc, folate, B12, protein) and the anti‑inflammatory compounds that temper platelet reactivity. It corrects iron deficiency without the ecological cost of haem iron from livestock. Meat is not required; its displacement by plants is itself a therapeutic intervention.

PLR is a number. It is also a narrative of inflammation and immunity, of nutritional status and neoplastic risk. Learn to read it – and then learn to act.

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Note on dietary recommendations on this site:

For the sake of our environment we adhere to the following dietary preference hierarchy:

1. Plant‑based

2. Fungi / algae / fermented

3. Biotechnology / lab‑grown / cultures

4. Dairy / eggs

5. Meat / fish / poultry (only if no effective alternative exists)

This approach reflects ecological responsibility, antibiotic stewardship, and the urgent need to reduce the environmental footprint of dietary recommendations.

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