Biochemical measurements

The participant had to fast for 12 hours and not to urinate 4 hours before the examination. 

Blood determinations: The fasting blood samples were drawn prior to ingestion of the glucose load.

• an EDTA-tube for haematological determinations (haematocrit) 
• a heparinized tube (15 ml) for plasma glucose and plasma creatinine determinations
• 4 ml serum tubes (for S-cholesterol and S-triglycerides determinations) and for the sample bank and 1-2 plasma tubes for the serum/plasma bank.

Furthermore, one hour after the ingestion of a glucose dose a blood sample was drawn for the determination of plasma glucose. Each person received a 20 % glucose dose graded (250-337 ml, 338-412 ml, 413-450 ml) according to the person’s size/body surface area which was estimated using a table of height and weight. Based on the plasma sample the 1-hour glucose tolerance test value was determined.

The heparinized tubes were centrifuged within half an hour, the serum tubes within one hour after the samples were drawn.  The samples were drawn by five laboratory nurses.

Haematocrit was determined in the field laboratory during the day the blood samples were drawn. The other determinations were made based on the frozen samples 1-3 weeks later in the Mobil Clinic central laboratory.

• Hkr: The sample drawn into an EDTA-tube was analyzed by the CLAY-ADAMS R microhaematocrit method. It was centrifuged for five minutes at a speed of 12 500 rpm (Takkunen 1976).
• Cholesterol: Serum cholesterol was determined in accordance with the manufacturer’s manual (Technicon AutoAnalyzer Methodology N-24 a 1965, Technicon AutoAnalyzer Methodology N-54, N-77 1969) using a modification of the Liebermann-Burchard method (Huang et al. 1961, Boy 1963). The variation coefficient (CV) indicating the repeatability was 0.02–0.04. In the light of control sera measurements (Kliinisten laboratoriotutkimusten laaduntarkkailu Oy) the results of the Mobile Clinic laboratory were close to the means of the other laboratories.  Using control sera the laboratory’s results were also compared with those reported by the US CDC on the same samples, and the results of the Mobile Clinic laboratory were about 5 % higher than those of the CDC.
• Triglycerides: Serum triglycerides were analyzed by an automatic method developed by the Mobile Clinic laboratory (Björkstén et al. 1972).
• Glucose: Plasma glucose (fasting and tolerance test value) was determined by a modification of the Hoffman ferricyanide method (Hoffman 1937, Technicon AutoAnalyzer Methodology N-2b, 1965) (Method folder 2.16). At the concentration 160 mg/100 ml the method yielded 5 % higher results than the enzymatic method. The reliability (CV) was 0.01 – 0.03. In comparison to other laboratories of the Helsinki control circle the Mobile Clinic laboratory yielded concentrations which were higher by 3 – 10 %. The US CDC concentrations using the enzymatic method were 5 % higher than those analyzed by the Mobile Clinic laboratory on the same samples.
• Creatinine: The creatinine concentration was determined from plasma samples by a modification of the Jaffe method (Technicon AutoAnalyzer Methodology N-11b, 1965). The analytic level of the Mobile Clinic laboratory was slightly higher than that of the other laboratories of the Helsinki control circle. The reliability was (CV) 0.02-0.05.
• Hormones of the thyroid gland: Serum T3 (N = 137), T3U (N = 106), and T4 (N = 1290) (Lamberg et al. 1970) were determined.

Determinations based on the urine samples: Women, men aged 50 or over, and those complaining of urinary tract symptoms provided a clean midstream urine sample, whereas men aged under 50 years provided a usual midstream urine sample. Albumin, glucose, blood and ketone bodies were qualitatively determined by test strips (Labstix). The urine bacteria were determined in women by culture on an Uricult test slide. Slides with a growth 104 or over were sent to the National Public Health Institute laboratory for typing and determination of antibiotic resistance. The diagnosis bacteriuria was based on two samples both with a growth of 105/ml or over (Kass 1956, Heinonen et al. 1968).