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Complete blood count-derived inflammatory indices summarize relationships among circulating neutrophils, lymphocytes, monocytes and platelets. NLR, PLR, MLR, SII, SIRI and AISI/PIV may describe the systemic inflammatory background of a patient with peri-implant disease, but they do not localize the source of inflammation and do not diagnose peri-implantitis.
From complete blood count to composite indices
A complete blood count provides the numerical components from which the indices are calculated. Neutrophils reflect rapid innate immune activity; lymphocytes represent adaptive and regulatory functions; monocytes connect the circulation with tissue macrophage and osteoclast-lineage biology; and platelets participate in haemostasis, endothelial signalling and thrombo-inflammation.
An index is a mathematical transformation of these counts rather than a separate laboratory test. The component values should therefore be examined before the final number is interpreted.
| Component | Biological context | Important limitation |
|---|---|---|
| Neutrophils | Rapid antimicrobial and innate inflammatory response. | Increase with acute infection, stress, trauma and corticosteroid exposure. |
| Lymphocytes | Adaptive immunity and immune regulation. | May decrease with stress, medication, acute illness or immune dysfunction. |
| Monocytes | Precursors of macrophages and osteoclast-lineage cells. | Affected by infection, inflammatory disease and haematological conditions. |
| Platelets | Haemostasis, endothelial interaction and leukocyte communication. | Altered by inflammation, iron status, medication and haematological disease. |
| WBC | Total circulating leukocyte burden. | Does not show which cell population drives the change. |
Formulas
| Index | Formula | Principal components |
|---|---|---|
| NLR | NEU / LYM | Neutrophils relative to lymphocytes |
| PLR | PLT / LYM | Platelets relative to lymphocytes |
| MLR | MON / LYM | Monocytes relative to lymphocytes |
| SII | PLT × NEU / LYM | Platelet-neutrophil axis relative to lymphocytes |
| SIRI | NEU × MON / LYM | Neutrophil-monocyte axis relative to lymphocytes |
| AISI/PIV | NEU × MON × PLT / LYM | Combined neutrophil, monocyte and platelet profile |
Absolute counts should be used with consistent units, commonly ×109/L. NLR, PLR and MLR are ratios. Composite indices depend on the numerical units entered, so values calculated from differently scaled inputs cannot be compared without conversion.
AISI is commonly expanded as aggregate index of systemic inflammation, while PIV is commonly expanded as pan-immune-inflammation value. Both labels are often applied to the same four-component formula. Because terminology and scaling vary across publications, the formula and input units should always be reported.
NLR: neutrophils relative to lymphocytes
NLR increases when neutrophils rise, lymphocytes fall, or both events occur. These mechanisms are not clinically equivalent. An elevated ratio may reflect infection, inflammatory stress, medication effects or a chronic systemic condition. In peri-implant research, NLR can characterize systemic inflammatory background, but it cannot identify the implant as the source.
PLR and the platelet-inflammatory axis
PLR combines platelet and lymphocyte counts. Platelets are active participants in endothelial signalling, leukocyte communication and inflammatory responses. PLR may change in inflammatory, vascular, metabolic and haematological conditions. Interpretation requires separate inspection of PLT and LYM.
MLR and the monocytic component
MLR emphasizes circulating monocytes relative to lymphocytes. Monocytes migrate into tissues and differentiate into macrophages; related lineages also contribute to osteoclast biology. MLR may therefore be relevant to chronic inflammatory research, although it remains nonspecific.
SII, SIRI and AISI/PIV
SII combines platelets, neutrophils and lymphocytes. SIRI combines neutrophils, monocytes and lymphocytes. AISI/PIV includes all four populations. These composite measures can distinguish patients with the same NLR but different monocyte or platelet counts.
Aggregation also increases sensitivity to confounding. A large numerical result does not demonstrate that a composite index is biologically superior or diagnostically more specific. Added value must be tested against simpler measures such as CRP, WBC and NLR and confirmed through external validation.
Worked calculation
Consider a CBC with NEU 5.6, LYM 1.4, MON 0.7 and PLT 280, all entered using the laboratory convention of ×109/L.
| Index | Calculation | Result |
|---|---|---|
| NLR | 5.6 / 1.4 | 4.0 |
| PLR | 280 / 1.4 | 200 |
| MLR | 0.7 / 1.4 | 0.50 |
| SII | (280 × 5.6) / 1.4 | 1120 |
| SIRI | (5.6 × 0.7) / 1.4 | 2.8 |
| AISI/PIV | (5.6 × 0.7 × 280) / 1.4 | 784 |
The arithmetic describes a neutrophil-predominant profile relative to lymphocytes, with additional monocyte and platelet contributions. It does not establish the anatomical source, duration or clinical importance of the inflammatory signal.
Peri-implant disease and systemic inflammation
Peri-implantitis is diagnosed from peri-implant clinical inflammation and progressive supporting bone loss. Blood findings are not part of the primary diagnostic definition.
A systematic review and meta-analysis reported higher serum CRP, IL-6 and WBC counts in peri-implantitis groups. The number of eligible studies was limited, and CRP estimates showed very high heterogeneity. A cross-sectional biochemical study also reported higher WBC counts in peri-implantitis after adjustment for periodontitis history. These findings support an association with systemic inflammatory burden but do not demonstrate that the implant lesion caused the blood changes.
Factors that can change the indices
- acute infection, fever, trauma or recent surgery;
- diabetes, obesity, cardiovascular disease, autoimmune disease or cancer;
- periodontitis and other inflammatory conditions;
- smoking, stress, sleep loss and intense exercise;
- corticosteroids, immunosuppressive therapy and other medications;
- dehydration, sampling time, laboratory method and unit convention.
There are no universally accepted peri-implantitis-specific thresholds for NLR, PLR, MLR, SII, SIRI or AISI/PIV. Cut-offs developed in oncology, cardiology or other populations should not be transferred directly into peri-implant diagnostics.
Integration with peri-implant assessment
- Define the local condition: assess bleeding on probing, suppuration, probing depths, plaque control, prosthetic cleansability and comparative radiographic bone levels.
- Review the CBC components: determine whether NEU, LYM, MON or PLT is responsible for the index value.
- Check competing explanations: document acute illness, chronic disease, smoking, medication and recent procedures.
- Calculate reproducibly: use predefined formulas and consistent units.
- Interpret in context: integrate the blood profile with local findings and longitudinal information.
Clinical and biological synthesis
- CBC-derived indices summarize relationships among circulating immune cells and platelets.
- The component counts explain why an index changed and should accompany the calculated value.
- Blood results may describe systemic inflammatory background but do not localize its source.
- No universal peri-implantitis-specific diagnostic cut-off has been established.
- The strongest current role of these indices is in research, standardized monitoring and validated multivariable risk models.
Download the full educational material
The extended PDF contains the complete formula table, component-level interpretation, a worked calculation, evidence boundaries and a structured clinical and research workflow.
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Selected references
- Berglundh T, Armitage G, Araujo MG, et al. Peri-implant diseases and conditions: consensus report of workgroup 4 of the 2017 World Workshop. Journal of Clinical Periodontology. 2018;45(Suppl 20):S286-S291.
- Schwarz F, Derks J, Monje A, Wang HL. Peri-implantitis. Journal of Clinical Periodontology. 2018;45(Suppl 20):S246-S266.
- Yan Y, Orlandi M, Suvan J, et al. Association between peri-implantitis and systemic inflammation: a systematic review. Frontiers in Immunology. 2023;14:1235155. PMID: 37691939.
- Blanco C, Linares A, Dopico J, et al. Peri-implantitis, systemic inflammation, and dyslipidemia: a cross-sectional biochemical study. Journal of Periodontal & Implant Science. 2021;51(5):342-351.
- Eraslan S, et al. Unraveling the clinical significance and prognostic value of NLR, PLR, SII and SIRI: an extensive literature review. 2024. PMID: 38343523.
- Peri-implantitis and systemic inflammation: current evidence, biological plausibility, and research gaps. Periodontology 2000. 2026. PMID: 42642953.
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This educational material does not replace individual clinical assessment, laboratory interpretation or medical consultation.
This work was co-funded by the European Union under grant agreement No. 2024-1-PL01-KA220-HED-000251208. Views and opinions expressed are those of the author(s) only and do not necessarily reflect those of the European Union or the Foundation for the Development of the Education System (FRSE). Neither the European Union nor FRSE can be held responsible for them.