Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.

[Q]: Abstract: We measured the activity of the enzyme porphobilinogen deaminase in red blood cells of 222 persons. Ninety-seven of 107 patients with acute intermittent porphyria had enzyme activity below the normal range, whereas 55 of 56 patients with other types of porphyria had normal activity. This underscores the utility of this test in confirming the diagnosis of acute intermittent porphyria. Measurement of enzyme activity in 41 families with acute intermittent porphyria demonstrated that deficient activity is inherited as an autosomal dominant trait. Many latent carriers of the genetic defect were identified by family studies, permitting appropriate precautions to avoid potentially lethal porphyric attacks.
[A]: Red blood cell porphobilinogen deaminase in the evaluation of acute intermittent porphyria [published erratum appears in JAMA 1987 Mar 13;257(10):1332]

[Q]: Abstract: To better understand declining autopsy rates, data have been gathered prospectively on 1080 consecutive deaths over six years among patients admitted to a medical intensive care/coronary care unit. Overall autopsy rate was 36%. Autopsy rates declined sharply with age from 60% for those aged 16 to 34 years to 23% for those 85 and over (P less than .001). The highest rates by diagnosis were aortic aneurysm (70%), hepatic failure (52%), heart rhythm disturbance (48%), pulmonary embolism (45%), and sepsis (41%). Patients receiving major procedures had a significantly higher autopsy rate (38 versus 29%, P less than .05) but rates bore little relation to prognoses given at admission by house officers, suddenness of death, sex, marital status or year of admission. Even among intensively treated patients, autopsy rates decline strikingly with age, demanding honest re-appraisal to restore the place of autopsy in medical education, clinical research, and quality of care assessment for an increasingly elderly population.
[A]: Age and the declining rate of autopsy.

[Q]: Abstract: The influence of the peptide chain length of partial enzymic hydrolysates of protein on nitrogen and amino acid absorption was studied in 12 subjects using a jejunal perfusion technique. Three hydrolysates of egg white and an equivalent amino acid mixture were perfused at 30 mmol/L and 100 mmol/L in two separate experiments. Two hydrolysates (OH1 and OH2) contained mainly dipeptides and tripeptides, whereas the third (OH3) comprised tripeptide to pentapeptides as judged chromatographically. Nitrogen absorption was significantly slower from the higher chain length mixture, OH3, than from the short chain mixtures, OH1 and OH2, at both concentrations. Similarly, several amino acid residues were absorbed less well from OH3 than from OH1 and OH2. These data demonstrate that the chain length of heterogeneous mixtures of peptides affects absorption of nitrogen and individual amino acid residues, and suggest that brush border hydrolysis of tetrapeptides and pentapeptides limits absorption from enzymic hydrolysates of protein which simulate the composition of the postprandial luminal contents.
[A]:
Effect of peptide chain length on absorption of egg protein hydrolysates in the normal human jejunum.