Serum samples

from 503 children submitted to the laboratory at the Department Selleck GDC-0068 of clinical biochemistry for analysis at Akershus University Hospital from December 2009 to January 2011 were collected. They were leftover volumes after clinical biochemistry analysis and were randomly picked out during the 14 months period. The children were born between 1998 and 2003 and were scheduled to have a DTaP-polio booster vaccination at the age of 7–8 years. Approximately half of the samples (46%) were from general practitioners (GPs), the rest were from in-patients. One third of the samples from the GPs lacked any information regarding diagnosis and medical records were not available. Medical records were checked for all in-patients, leading to the exclusion of five patients suffering from diagnoses likely BI 2536 supplier to cause immunodeficiency (acute lymphatic leukaemia, lymphoma, former spleen extirpation). The two dominating indications for sampling were allergy

investigation and acute infection, followed by unspecified stomach pain, neurological/psychiatric disease and endocrine disorders. A total of 498 children were thus included. Date of blood sampling and date of birth and personal identification number for each person were recorded, and linked to the Norwegian Immunisation Registry (SYSVAK) to obtain the vaccine through history and to calculate the number of days between last pertussis booster and blood sampling. The study was approved by the Norwegian Regional Committee for Medical Research Ethics. The childhood pertussis

vaccination program in Norway consists of three doses of DTaP-polio at 3, 5 and 12 months of age, containing the pertussis antigens pertussis toxoid, filamentous haemagglutinin (FHA) and pertactin (Prn) (Infanrix-polio, GSK). At the age of 7–8 years the children are offered a booster dose consisting of pertussis toxoid and FHA (Tetravac, Sanofi Pasteur MSD). Anti-PT IgG antibodies were analysed using a validated in-house enzyme-linked immunosorbent assay (ELISA) slightly modified from previous publications [15] and [16]. Briefly, PT (List Biological labs, CA, USA) was coated to 96 wells micro-titer plates at 1 μg/ml in 0.05 M bicarbonate buffer pH 9.6 for 48 h at 4 °C. Blocking was performed with 250 μL 1% powdered skimmed milk (Oxoid, UK) in PBS for 30 min at room temperature. Two-fold serial dilutions of patients sera were analysed, and bound antibody was detected with an anti-human IgG (gamma chain-specific) alkaline phosphatase conjugate (Sigma, USA). The WHO International Standard Pertussis Antiserum (NIBSC 06/140) was used to generate the standard curve. Interpolation of unknown sera was done by four-parameter curve analysis (Softmax Ver. 2.