Determination of pediatric reference limits for 10 commonly measured autoantibodies

OBJECTIVES

The objective of this study was to establish pediatric reference limits for autoimmune disease markers in the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort of healthy children and adolescents to support their interpretation and clinical decision making. The CALIPER is a national study of healthy children aiming to close gaps in pediatric laboratory medicine by establishing a robust database of pediatric reference intervals for pediatric disease biomarkers (caliperdatabase.org).

METHODS

Healthy children and adolescents (n=123, aged 1-19) were recruited to CALIPER with informed consent. Serum autoantibody testing conducted on the BIO-FLASH analyzer (Werfen, Barcelona, Spain) included anti-dsDNA IgG, anti-Sm IgG, anti-RNP IgG, anti-SSB/La IgG, anti-Ro60 IgG, anti-Ro52 IgG, anti-cardiolipin IgG, anti-MPO IgG, anti-PR3 IgG, and anti-tTG IgA. Pediatric reference limits representing 95th, 97.5th, and 99th percentiles were calculated using the non-parametric rank method according to Clinical Laboratory Standards Institute C28-A3 guidelines.

RESULTS

The proportion of samples with results above the lower limit of the analytical measuring range were: anti-cardiolipin IgG 90%, anti-dsDNA 22%, anti-Sm 13%, anti-RNP 0.8%, anti-SSB/La 0%, anti-Ro60 0%, anti-Ro52 0%, anti-MPO 25%, anti-PR3 9%, and anti-tTG IgA 28%. Pediatric reference limits and associated 90% confidence intervals were established for all 10 markers. All autoantibodies could be described by one age range except for anti-cardiolipin IgG and anti-MPO. A sex-specific difference was identified for anti-tTG IgA.

CONCLUSIONS

Robust pediatric reference limits for 10 commonly clinically utilized autoimmune markers established herein will allow for improved laboratory assessment and clinical decision making in pediatric patients using the BIO-FLASH assay platform worldwide.

Sustaining continuous ambulatory peritoneal dialysis after herniotomy

Controversy still exists as to whether peritoneal dialysis (PD) treatment can be safely continued after herniotomy. Many nephrologists withhold PD treatment for several weeks after herniotomy for fear of dialysate leakage and hernia recurrence. Here, we report on 9 patients (2 women, 7 men) in whom herniotomy was performed for umbilical (n = 3), inguinal (n = 5), or cicatricial hernia (n = 2), or for open processus vaginalis (n = 2). Surgery was performed according to the Lichtenstein method with insertion of a polypropylene mesh and ligation of the hernia sac. In all patients, PD treatment was paused for the day of surgery and for 1-3 days postoperatively, depending on residual renal function. Over the next several days, low-volume (1.0-1.5 L), high-frequency (6 per day) exchanges were started. The patient's original PD regimen was gradually reinstated over the next 2-4 weeks. All patients recovered rapidly, with no uremia or dialysis-related complications. Particularly, no leakage and no hernia recurrence could be observed 3 months thereafter. None of the patients had to be hemodialyzed intercurrently. In conclusion, continuing a modified regimen of CAPD treatment after herniotomy seems to be safe, with excellent patient comfort.

Phthalic acid is the main metabolite of the plasticizer di(2-ethylhexyl) phthalate in peritoneal dialysis patients

Di(2-ethylhexyl) phthalate (DEHP) is the most commonly used plasticizer in polyvinyl chloride (PVC) plastics, and is therefore a major constituent of continuous ambulatory peritoneal dialysis (CAPD) bags. Because DEHP is not chemically bound, it leaches out of the plastic matrix. Recently, we found that leukocyte function in vitro is impaired by a mixture of metabolites of DEHP. In the present study, we investigated the metabolism of DEHP in patients on CAPD. The study group consisted of 10 stable patients, on CAPD for at least 6 months, using a plasticizer-containing PVC PD system [ANDY Plus (Fresenius Medical Care, Bad Homburg, Germany)]. Effluent dialysate and urine samples were collected over 24 hours, and a 10 mL blood sample was drawn. Concentrations of DEHP and its metabolites mono(2-ethylhexyl) phthalate (MEHP), phthalic acid (PA), and 2-ethylhexanol (2-EH) were determined in urine, dialysate, and serum using gas chromatography/mass spectrometry. Additionally, the degree of glucuronidation of the phthalic acid esters in urine were determined. In serum, dialysate, and urine, PA was the predominant metabolite of DEHP (0.205 +/- 0.067 mg/L, 0.284 +/- 0.180 mg/L, and 1.34 +/- 1.00 mg/L, respectively), but concentrations of MEHP were low (0.0100 +/- 0.0056 mg/L, 0.022 +/- 0.008 mg/L, 0.011 +/- 0.0064 mg/L, respectively). Urinary MEHP was glucuronidated to approximately 15%. PA was 35% eliminated as a glucuronide. Unlike healthy subjects, PD patients do not eliminate DEHP mainly in the form of MEHP or MEHP metabolites. They further break these compounds down to PA. The fact that concentrations of PA in urine exceed by far the respective serum concentrations indicates that PA is secreted by the kidney. Further research on the toxicological aspects of plasticizers in uremic patients should take these findings into account.

[Cervical actinomycosis in systemic lupus erythematosus, nephrocalcinosis and distal renal tubular acidosis (type I-RTA)]

HISTORY AND CLINICAL FINDINGS

A 25-year-old woman presented with a painful soft-tissue swelling in the right neck, which made it impossible to assess the right cervical lymph nodes, while other lymph nodes were unremarkable on palpation. For 9 years she had been known to have polyarthritis. All joints were freely mobile and were without deformity or inflammatory signs. Flexion of the left elbow was slightly painful but freely mobile. There was no skin rash.

INVESTIGATIONS

Erythrocyte sedimentation rate was 44 mm/h, there was a leucocytosis of 16,000 granulocytes/ml. There was hypokalaemia (3.5 mEq/l) and a metabolic hyperchloremic acidosis with a pH of 7.27 and a urinary pH of 6.5. Antinuclear and anti-ds-DNA antibodies were raised (ANA: 3.9 multiple of cutoff point [MOC; normal: 0-1.0]; anti-ds-DNA antibodies: 4.0 [normal: 0-1.0])-Fine needle aspiration cytology from the swelling revealed erythrocytes, double-refractory horny lamellae, cellular debris and only a few inflammatory cells. Abdominal ultrasound showed nephrocalcinosis. Microbiological cultures were negative.

DIAGNOSIS, TREATMENT AND COURSE

Assuming a bacterial cause of the swelling antibiotic treatment with Phenoxymethylpenicillin (4 MU/d) was initiated. The local findings rapidly improved and the inflammatory parameters regressed to normal. 16 weeks after the initial admission the abscess recurred and biopsy now revealed actinomycetes with typical granules, confirming cervical actinomycosis. The other symptoms indicated autoimmune disease and, together with previous findings, established the additional diagnosis of lupus erythematodes, which caused the type 1 distal tubular acidosis.

CONCLUSIONS

This case illustrates the basic approach of establishing an all-encompassing diagnosis that brings together seemingly isolated findings. It is especially in systemic disease that such diagnostic strategy will frequently lead to its recognition.

Severe thrombocytopenia and response to corticosteroids in a case of nephropathia epidemica

Nine days after working in the woods, a previously healthy 32-year-old man fell seriously ill. His symptoms included high fever, chills, diffuse myalgia, severe headache, and back pain. On the fifth day of onset of symptoms, blood tests showed creatinine levels of 5.4 mg/dL accompanied by marked proteinuria. After admission to the hospital, a diagnosis of nephropathia epidemica (NE) caused by Puumala virus was made using solid-phase enzyme-linked immunosorbent assay (ELISA). The patient gradually recovered renal function without requiring dialysis. However, he surprisingly experienced a sharp decline in platelet count to a minimum of 2,000/microL with concomitant occurrence of petechiae and conjunctival hemorrhage. Prednisolone was initiated, resulting in a swift rise in platelets. Six days later, when the medication was withdrawn, a sharp decrease in platelets recurred. The steroids were then readministered for the next 3 months, thus reestablishing a stable platelet count. The immediate rise of platelets after administration of prednisolone supports the pathophysiological view of hantavirus infection as an immunologically mediated disease. Corticosteroids in the treatment of hantavirus-associated thrombocytopenia might need further systematic evaluation.