The serum concentration of YKL-40, a matrix protein of specific granules in neutrophils, was determined by RIA in 90 patients hospitalized with pneumonia of suspected bacterial origin. Of these, 64 were followed prospectively during antibiotic treatment with blood samples taken on day 0 (on admission and the start of treatment) and on days 1, 3, 5, 7, 10, and 21. Serum YKL-40 at admission was increased in patients with Streptococcus pneumoniae pneumonia (median, 893 microgram/L; 95% confidence interval [CI], 704-1560), compared with healthy subjects (median, 102 microgram/L; 95% CI, 64-247 microgram/L; P<.001) and in patients with pneumonia of unknown etiology (median, 448 microgram/L; 95% CI, 334-700; P<.05). Peak YKL-40 serum values were observed on day 1 and thereafter declined steeply to almost normal by day 3. During the first 10 days, there was a close relation between serum YKL-40 and markers of specific granules of neutrophils (serum lactoferrin and neutrophil gelatinase-associated lipocalin), which suggests that serum YKL-40 reflects exocytosis of specific granules of neutrophils in persons with acute bacterial pneumonia.

Serum YKL-40 is elevated in patients with SSc with pulmonary involvement.

No abstract

Genetic epidemiological studies of Autism Spectrum Disorders (ASDs) based on twin pairs ascertained from the population and thoroughly assessed to obtain a high degree of diagnostic validity are few. All twin pairs aged 3-14 years in the nationwide Danish Twin Registry were approached. A three-step procedure was used. Five items from the "Child Behaviour Checklist" (CBCL) were used in the first screening phase, while screening in the second phase included the "Social and Communication Questionnaire" and the "Autism Spectrum Screening Questionnaire". The final clinical assessment was based on "gold standard" diagnostic research procedures including diagnostic interview, observation and cognitive examination. Classification was based on DSM-IV-TR criteria. The initial sample included 7,296 same-sexed twin pairs and, after two phases of screening and clinical assessment, the final calculations were based on 36 pairs. The probandwise concordance rate for ASD was 95.2% in monozygotic (MZ) twins (n=13 pairs) and 4.3% in dizygotic (DZ) twins (n=23 pairs). The high MZ and low DZ concordance rate support a genetic aetiology to ASDs.

It has been hypothesized that prenatal exposure to testosterone may be associated with traits of attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD). We conducted a population-based study of dizygotic female twins to elucidate this hypothesis, assuming that the sex of the co-twin influences the level of prenatal exposure to testosterone. We invited parents of 24,552 3- to 15-year-old twins to answer questionnaires on traits of ADHD and ASD. We analysed the data using a proportional odds model with sex of the co-twin as an instrumental variable for prenatal exposure to testosterone of female twins. We received responses for 6,339 girls from dizygotic twin pairs. Odds ratios for male versus female co-twin were 0.71 (95 % confidence interval 0.61-0.81) for ADHD traits and 0.74 (0.66-0.83) for ASD traits, indicating that a twin brother reduces traits of ADHD and ASD in females. In conclusion, we found that female twins with a twin brother scored significantly lower in parent-reported traits of ADHD and ASD than those with a twin sister. The reason for this may be parental reporting bias, or confounding by unmeasured variables, or a causal effect of an intrauterine environment modified by the sex of the co-twin in the opposite direction of what we expected.