Abstract
This cohort study assesses whether an association exists between biologic treatment for hidradenitis suppurativa and neutrophil-lymphocyte ratio, platelet-lymphocyte ratio, and monocyte-lymphocyte ratio.
Hidradenitis suppurativa (HS) is a systemic inflammatory disorder associated with comorbidities, including cardiovascular disease.1 Systemic inflammation is thought to represent a shared mechanistic link between HS and comorbidities.1 Neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and monocyte-lymphocyte ratio (MLR) are biomarkers of systemic inflammation and risk factors for major adverse cardiac events.2,3 Blood counts and ratios have been evaluated in HS as disease severity biomarkers; however, to our knowledge, response to treatment has not been investigated.4 The aim of the study was to ascertain whether NLR, PLR, and MLR represent simple biomarkers for the assessment of systemic inflammation in HS and whether these biomarkers may be modified by treatment.
Methods
We performed a retrospective cohort study of 100 consecutive patients at a specialty HS clinic at St Vincent’s University Hospital over 4 months (November 4, 2020, to March 3, 2021). We collected data on blood count, C-reactive protein (CRP) level, patient demographic characteristics (including patient-reported race), smoking status, Hurley stage, and treatment. We also retrospectively reviewed laboratory results (obtained at baseline and week 12) for 15 biologic-naive patients who participated in a clinical trial of adalimumab therapy (EudraCT Identifier: 2016-001566-28). In accordance with the St Vincent’s Healthcare Group Medical Research Ethics Committee, this study was exempt from review and the informed consent requirement waived as data were collected during routine care. We followed the STROBE reporting guideline.
The t test was used to compare NLR, PLR, and MLR in patients receiving biologics vs other treatments; Spearman correlation test for associations of CRP level with NLR, PLR, and MLR; and paired t test to compare patients at baseline and week 12 of adalimumab. Statistical analysis was performed from March 4 to 31, 2021, using SPSS Statistics, version 27.0 (IBM Corp). A 2-sided P < .05 was considered statistically significant.
Results
The study included 100 patients; demographic characteristics, smoking status, Hurley stage, and treatments are outlined in Table 1. No patients had a hematological disorder. Overall, the mean NLR was 2.49 (95% CI, 1.14-3.84), mean PLR was 138.76 (95% CI, 88.93-188.59), and mean MLR was 0.30 (95% CI, 0.18-0.42) (Table 2). The mean NLR and PLR were significantly lower in patients receiving biologics vs other treatments (NLR: 1.99 [95% CI, 1.19-2.79] vs 2.66 [95% CI, 1.20-4.12]; P = .005; PLR: 120.93 [95% CI, 76.80-165.06] vs 144.71 [95% CI, 94.23-195.19]; P = .03) (Table 2). The NLR (r = 0.16; P = .12), PLR (r = −0.06; P = .12), and MLR (r = 0.003; P = .98) were independent of CRP level. In patients receiving adalimumab as part of a clinical trial, there was a significant reduction in NLR and PLR but not MLR from baseline to week 12 (Table 2).
Table 1. Patient Demographic Characteristics, Smoking Status, Hurley Stage, and Treatments.
| Characteristic | No. (n = 100) |
|---|---|
| Age, mean (SD), y | 38.6 (10.1) |
| Sex | |
| Female | 79 |
| Male | 21 |
| Race | |
| Asian | 2 |
| Black | 1 |
| White | 97 |
| Smoking status | |
| Active | 46 |
| Former | 14 |
| Never | 34 |
| Not documented | 6 |
| Hurley stagea | |
| 1 | 13 |
| 2 | 62 |
| 3 | 25 |
| Treatment | |
| Biologic | 25 |
| Metformin | 18 |
| Metformin and spironolactone | 11 |
| Spironolactone | 9 |
| Rifampicin-clindamycin | 9 |
| No treatment | 7 |
| Tetracycline antibiotics | 7 |
| Eumovate cream | 3 |
| Metformin and rifampicin-clindamycin | 3 |
| Acitretin | 2 |
| Metformin and tetracycline antibiotic | 2 |
| Liraglutide and minocycline | 1 |
| Metformin, spironolactone, and lymecycline | 1 |
| Dapsone | 1 |
| Dapsone and metformin | 1 |
| Biologics | |
| Adalimumab | 13 |
| Ustekinumab | 6 |
| Infliximab | 4 |
| Brodalumab | 2 |
The Hurley staging system is used to characterize the extent of hidradenitis suppurativa; stage 1 represents mild disease with single nodules or abscesses that heal without the formation of scarring or sinus tracts, stage 2 represents moderate disease with nodules or abscesses that heal with the formation of scarring and sinus tracts, and stage 3 represents severe disease with confluent areas of scarring and sinus tracts covering an entire anatomical area.
Table 2. NLR, PLR, and MLR in All Patients, Patients Receiving Biologics, and Before and After Treatment With Adalimumab.
| Ratio | Mean (SD) [95% CI] | P valuea | Adalimumab, mean (SD) [95% CI] | P valueb | |||
|---|---|---|---|---|---|---|---|
| All patients | Biologics | Other treatments | Baseline | Week 12 | |||
| NLR | 2.49 (1.35) [1.14-3.84] | 1.99 (0.80) [1.19-2.79] | 2.66 (1.46) [1.20-4.12] | .005 | 2.98 (0.89) [2.09-3.87] | 1.99 (0.72) [1.27-2.71] | <.001 |
| PLR | 138.76 (49.83) [88.93-188.59] | 120.93 (44.13) [76.80-165.06] | 144.71 (50.48) [94.23-195.19] | .03 | 147.25 (40.01) [107.24-187.26] | 110.59 (36.94) [73.65-147.53] | <.001 |
| MLR | 0.30 (0.12) [0.18-0.42] | 0.27 (0.09) [0.18-0.36] | 0.31 (0.13) [0.18-0.44] | .08 | 0.28 (0.08) [0.20-0.36] | 0.31 (0.21) [0.10-0.52] | .43 |
Abbreviations: MLR, monocyte-lymphocyte ratio; NLR, neutrophil-lymphocyte ratio; PLR, platelet-lymphocyte ratio.
Comparison between patients receiving biologics and any other treatment using t test.
Comparison between baseline and week 12 using paired t test.
Discussion
Hematologic parameters are an HS severity biomarker, but, to our knowledge, this study was the first to evaluate the response of these biomarkers to treatment. The NLR and PLR were significantly lower in patients receiving biologics, whereas the MLR was not. This finding was confirmed in the cohort of patients before and after treatment with adalimumab. The lower NLR and PLR in patients receiving biologics suggest the role of medical intervention in modifying systemic inflammation in HS. In rheumatoid arthritis, tumor necrosis factor inhibitors are thought to reduce cardiovascular disease risk by reducing systemic inflammation with emerging evidence in psoriasis.5,6 Study limitations include the small sample size, retrospective nature, and lack of generalizability beyond a hospital-based population with moderate to severe HS. The inherent bias associated with analysis of patients with severe disease who were more likely to receive biologics is mitigated by our assessment of biologic-naive patients receiving adalimumab therapy. This study provides initial evidence of an association between biologic treatment of HS and a reduction in the NLR and PLR, which are biomarkers of systemic inflammation. Further studies are needed to validate the hypothesis that biologic treatment can modify these biomarkers.
Data Sharing Statement
References
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Supplementary Materials
Data Sharing Statement
