Measurement of serum angiotensin-converting enzyme (ACE) activity can be helpful in the diagnosis and disease monitoring of sarcoidosis. Elevated serum ACE activity is found in 60-70% of sarcoidosis patients. Usually, the ACE activity is mildly increased (<3-fold the upper limit of the reference range) in sarcoidosis patients. Extremely elevated ACE activity is suggestive of the benign condition known as 'familial hyperactivity of ACE'. Familial hyperactivity of ACE is a relatively rare condition and can be confirmed by genetic testing. Considering a genetic cause of strongly elevated serum ACE activity is important to prevent possible overdiagnostics. Here, we highlight the factors that may complicate the interpretation of serum ACE activity measurements, and we present two cases that illustrate the importance of interdisciplinary consultation when extremely elevated serum ACE activity is measured.

Background: Lactose intolerance is defined as the presence of gastrointestinal symptoms, such as bloating, abdominal pain or diarrhoea, after consumption of lactose in individuals with lactose malabsorption. Most cases involve primary lactose intolerance, caused by a loss of activity of the enzyme lactase, needed for digestion of lactose. A traditional method of establishing lactose intolerance is the hydrogen breath test (HBT), accompanied by a questionnaire to document complaints experienced by the patient during the test. Due to knowledge on lactase-persistent alleles, DNA genotyping has become available for the diagnostic work-up for lactose intolerance. Both methods are currently in use. The aim of this study is to provide a definite diagnostic approach for patients suspected of lactose intolerance in a Dutch population. Methods: In this retrospective, observational study, patients aged 15 years or older were included after presenting to their treating physician with symptoms suggestive of lactose intolerance. HBT, including a questionnaire to document complaints and DNA genotyping of LCT-13910C/T was performed for each patient as part of a routine diagnostic work-up. Results: 1101 patients were included (29% men). Positive and negative predictive value, sensitivity and specificity of HBT vs. DNA genotyping were 80% (CI 75-84), 97% (CI 96-98), 89% (CI 84-92) and 94% (92-96) respectively. The use of the questionnaire added little diagnostic value. Conclusions: In a population with a high-prevalence of lactase-persistent alleles, we advice to exclude HBT from the diagnostic route for suspected lactose intolerance, and replace it with genotyping of lactase-persistent alleles.