An observational study in Knee Osteoarthritis and Osteoarthritis, sponsored by Utku Gürhan. Not yet recruiting at 1 site in Cyprus. Open to participants aged 40 Years to 60 Years. Per ClinicalTrials.gov, last updated 2026-06-23.
Sponsored by Utku Gürhan · Observational
Intra-articular platelet-rich plasma (PRP) injection is a widely used treatment for knee osteoarthritis, but patients respond to it very differently and there is currently no simple, inexpensive way to predict who will benefit. The neutrophil-to-lymphocyte ratio (NLR) and related indices derived from a routine complete blood count reflect a person's baseline inflammatory state. This prospective single-arm observational cohort study investigates whether the baseline NLR, together with the platelet-to-lymphocyte ratio (PLR), the systemic immune-inflammation index (SII), and the monocyte-to-lymphocyte ratio (MLR), predicts the clinical response to intra-articular PRP in patients with Kellgren-Lawrence grade 2 to 3 knee osteoarthritis. The investigators will enroll 120 patients aged 40 to 60 years, each of whom receives a standardized course of three leukocyte-poor PRP injections one week apart. Patients are followed for 6 months, and the primary clinical outcome is the change in the WOMAC osteoarthritis index at 6 months. Outcome assessors are blinded to patients' blood-count values. If a baseline blood ratio predicts response, it could become a low-cost tool to guide patient selection for PRP.
Background and Rationale: Intra-articular platelet-rich plasma (PRP) is increasingly used for symptomatic knee osteoarthritis, but the clinical response is highly variable and no inexpensive, routinely available biomarker currently guides patient selection. Recent work indicates that the peripheral-blood inflammatory phenotype is associated with PRP response (Tonutti et al., 2025) and that the absolute neutrophil count is an independent early-response predictor (De Luca et al., 2025). However, simple complete-blood-count-derived ratios such as the neutrophil-to-lymphocyte ratio (NLR) have not been tested prospectively for this purpose. This study addresses that gap with a pragmatic, low-cost translational biomarker design.
Design: Prospective, single-arm, observational cohort study. Outcome assessors are blinded to patients' blood-count values; patients are not informed of their NLR; statistical analysis is conducted blinded.
Population and Setting: 120 patients aged 40 to 60 years with symptomatic Kellgren-Lawrence grade 2 to 3 knee osteoarthritis and a body mass index below 40, recruited over a 4-month window (target 30 enrollments per month) from the Department of Orthopaedics and Traumatology, University of Kyrenia, Dr. Suat Gunsel Hospital. Approximately 180 patients are anticipated to be screened, with a target of 102 completed, analyzable participants after an estimated 15 percent attrition.
Intervention (uniform, per protocol): Each participant receives three leukocyte-poor PRP injections at one-week intervals. PRP is prepared by manual double-spin centrifugation (soft spin 1500 rpm for 5 minutes, then hard spin 3300 rpm for 10 minutes) from 20 mL of whole blood per session (total 60 mL per patient across the three sessions), anticoagulated with 8.5 percent ACD-A, without exogenous activation, targeting a 4 to 6 fold platelet concentration. Injections are delivered under ultrasound guidance via a superolateral approach with skin infiltration of 1 percent lidocaine. A 48-hour restriction on non-steroidal anti-inflammatory drugs is applied after each injection.
Biomarkers: The primary predictor is the baseline NLR. Secondary predictors are PLR, SII, and MLR; tertiary predictors are C-reactive protein and erythrocyte sedimentation rate. All are derived from a routine baseline complete blood count.
Outcomes: The primary clinical outcome is the change in WOMAC total score at 6 months. Treatment response is defined a priori as at least 30 percent improvement in WOMAC together with fulfilment of the OMERACT-OARSI responder criteria. Clinical assessments occur at baseline and at 1, 3, and 6 months.
PRP Product Characterization: Quality control is performed in two tiers. Tier 1 (all 120 patients, all 360 batches) records the final platelet concentration, the total leukocyte count, and the final volume. Tier 2, a pre-specified validation subset of approximately 40 patients (the first 20 consecutive patients plus every fifth subsequent patient, approximately 120 batches), additionally records the leukocyte differential and erythrocyte contamination.
Statistical Analysis and Sample Size: The primary analysis is a multivariable linear regression of 6-month WOMAC change on baseline NLR, adjusted for age, body mass index, Kellgren-Lawrence grade, and baseline WOMAC. A secondary analysis evaluates the discriminative performance of baseline NLR for responder status by receiver operating characteristic analysis. For the primary regression (alpha 0.05, power 0.80, one numerator degree of freedom, five predictors, effect size f-squared 0.10), 82 participants are required; the secondary analysis requires 95. To satisfy both, the enrollment target is 120, anticipating 102 completers.
Ethics and Reporting: Ethics approval is sought from the Girne University Clinical Research Ethics Committee. Reporting follows the STROBE and REMARK recommendations, and the protocol follows SPIRIT guidance.
3,292 studies on the registry are indexed under Osteoarthritis, Knee; 623 are open to participants now.
This study's planned enrollment of 120 is above the median of 100 across 486 observational studies indexed under Osteoarthritis, Knee.
Browse Osteoarthritis, Knee studies →Utku Gürhan is the lead sponsor of 3 studies on the registry; 1 is open to participants now.
Counted across the registry records on this site, refreshed daily.
Adult patients aged 40 to 60 years presenting to the orthopedic clinic of the University of Kyrenia, Dr. Suat Gunsel Hospital, with symptomatic primary knee osteoarthritis of Kellgren-Lawrence grade 2 or 3, who are candidates for and scheduled to receive a course of intra-articular platelet-rich plasma for the index knee.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Change in WOMAC total score at 6 months
Change from baseline in the total score of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at 6 months after the first injection. The primary analysis is a multivariable linear regression testing the baseline neutrophil-to-lymphocyte ratio (NLR) as the predictor of interest, adjusted for age, body mass index, Kellgren-Lawrence grade, and baseline WOMAC score.
Time frame: Baseline to 6 months
Treatment response at 6 months (responder versus non-responder)
Treatment response is defined a priori as at least 30 percent improvement in WOMAC total score together with fulfilment of the OMERACT-OARSI responder criteria. The discriminative performance of the baseline NLR for responder status is assessed by receiver operating characteristic analysis with the optimal threshold identified by the Youden index.
Time frame: Baseline to 6 months
Predictive value of PLR, SII, and MLR for 6-month WOMAC change
Association of the baseline platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and monocyte-to-lymphocyte ratio (MLR) with the change in WOMAC total score at 6 months, evaluated by multivariable regression.
Time frame: Baseline to 6 months
Change in WOMAC total score at 1 and 3 months
Change from baseline in WOMAC total score at the 1-month and 3-month assessments, describing the trajectory of clinical response.
Time frame: Baseline to 1 month and to 3 months
Change in knee pain on a Visual Analogue Scale
Change from baseline in knee pain on a Visual Analogue Scale at the 1-month, 3-month, and 6-month assessments.
Time frame: Baseline to 1, 3, and 6 months
Change in the Knee injury and Osteoarthritis Outcome Score (KOOS)
Change from baseline in the Knee injury and Osteoarthritis Outcome Score (KOOS) subscale scores at 6 months.
Time frame: Baseline to 6 months
Association of baseline CRP and ESR with treatment response
Exploratory association of the baseline C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) with 6-month treatment response.
Time frame: Baseline to 6 months
Platelet-rich plasma product characterization
Two-tier quality control of the PRP product. Tier 1 (all 120 patients, all 360 batches): final platelet concentration, total leukocyte count, and final volume. Tier 2 (a pre-specified validation subset of approximately 40 patients, approximately 120 batches): leukocyte differential and erythrocyte contamination.
Time frame: At the three injection sessions (study weeks 1, 2, and 3)
Plan to share: No
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