13. Point-of-Care Creatinine Testing in High-Risk Patients

In some circumstances, a creatinine check at home instead of a complete clinical control could be sufficient for patients with renal disease. Home monitoring of serum creatinine concentrations could, for instance, be useful during insecure periods after kidney transplantation, or to keep a close watch on possible disease recurrences. Below we describe a pediatric case of recurrent hemolytic-uremic syndrome (HUS), in which we would have liked to monitor creatinine levels at home in order to restrict the number of hospital visits. Point-of-care testing (POCT) for creatinine concentrations offers the advantage of providing a result within minutes outside the hospital, which potentially enables faster diagnosis and management of HUS and other conditions threatening kidney function. Obviously, POCT devices employed at home must be easy to use in daily practice by the patient or his/her parents. Therefore, it was considered essential that tests could be carried out with a small volume of capillary blood. Notably, POCT systems used at home should produce results comparable to reference testing in the laboratory. To that purpose, we evaluated two different POCT systems for creatinine measurement (Roche Reflotron Plus and Abbott i-STAT) versus the routine test used in the laboratory of the Erasmus MC-Sophia Children’s Hospital, in 20 children displaying an extensive range of creatinine blood values. Children with atypical HUS have frequently been referred to the pediatric clinic in Rotterdam. This syndrome is characterised by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure (1). A representative case described below gave rise to the present data. 13.1. 1 Case history At the age of four months, a boy presented with atypical HUS for the first time. Plasma exchange resulted in temporary clinical improvement, but the HUS recurred after a few months, and plasmapheresis could not prevent him from progression to end-stage renal failure. Peritoneal dialysis was started, yet after two years this was switched to hemodialysis due to a devastating peritonitis. Bilateral nephrectomy was performed at four years of age because of therapy-resistant hypertension. Finding a suitable deceased kidney donor was difficult due to the patient’s homozygosity on HLA-A, -B and -DR alleles. At the age of five years, the boy received an adult deceased donor kidney graft. Post-transplant, serum creatinine values quickly normalised to circa 25 µmol/L (see Figure 13.1.). Ten days post-transplant he showed perforation of the colon ascendens, for which a temporary stoma was applied. One month post-transplant, an acute rejection occurred, which was successfully treated with methylprednisolone. Subsequently, with monthly intervals, two episodes of bacterial gastroenteritis with increased serum creatinine concentrations due to dehydration, and a primo Epstein-Barr virus infection occurred. A quiet period of ten months ensued. Figure 13.1. Case history: patient serum creatinine concentrations in time. Each data point represents a single serum creatinine concentration obtained by routine laboratory measurement (Y-axis) at the age indicated (X-axis). Bold horizontal lines represent the reference . At the age of 6 1/2 years the patient displayed a sudden increase in serum creatinine concentration, along with hematuria. A graft biopsy was suspect for recurrence of HUS. The boy was treated by plasma exchange, daily during the first two weeks, followed by tapering in frequency, and after three months he was switched to weekly plasma infusions. During this treatment, serum creatinine values suddenly deteriorated, after which hemodialysis was restarted. At seven years of age, a second transplantation was performed using a kidney from the patient’s mother. After problems with urinary drainage followed by reimplantation of the graft ureter, serum creatinine concentration settled at about 120 µmol/L. However, eleven months post-transplant another sudden, biopsy-proven recurrence of HUS occurred, with a rise in serum creatinine to approximately 700 µmol/L. Daily plasma exchanges resulted in reversal of the creatinine concentration to pre-recurrence level, and the frequency was very slowly tapered to twice every week. Two further episodes of rising serum creatinine concentration were seen, due to gastroenteritis and dehydration. Ideally, the patient would have been checked by the physician on an almost daily basis. However, as the boy lived at a distance of about 50 km from our clinic and went to school normally, this was not feasible for him and his parents. To save the family anxiety and several trips to the hospital, we intended to optimise care by checking the boy’s blood creatinine value at home.