[Diagnostic yield of various urine tests in urinary tract infections]

OBJECTIVES

1. To determine the value of pyuria and bacteriuria by high-power field (hpf) in centrifuged urine and of tests with reactive strips for determining leukocyte estearase activity and nitrites in the diagnosis of urinary tract infection (UTI). 2. To establish the ideal cut-off point for these tests.

DESIGN

Comparative survey.

SETTING

Second level health care unit of the Instituto Mexicano del Seguro Social.

PATIENTS AND METHODS

A total of 105 patients were prospectively studied, with or without urinary symptoms, seen in the emergency ward.

MEASUREMENTS

A clinical history and physical exploration was done in each patient. A urine sample was used for microscopic analysis for determining leukocytes and bacteria using hpf microscopy; the urine leukocytes count was assayed as well as leukocyte estearase and nitrites using reactive strips. All samples were subjected to urine culture. Urine samples were obtained using a Nelaton probe in 65% of the patients and the rest using the midstream urination technique.

RESULTS

Forty patients (38%) were identified as UTI cases based on clinical and laboratory criteria (urine culture and leukocyte count). The best cut-off point for number of leukocytes was 8 per hpf and for bacteriuria it was 2+ per hpf and for leukocyte estearase it was 1+. The sensitivity, specificity and predictive values of the pyuria hpf, bacteriuria by hpf and leukocyte estearase by reactive strip were comparable. The nitrites had a lower sensitivity than the other tests (p < 0.05). The negative predictive value of the nitrites was less than the microscopic bacteriuria (74% vs 85%, p = 0.005). The combination of positive tests in leukocytes and bacteriuria increased the specificity and the positive predictive value (99% and 96% respectively) when compared to the individual tests.

CONCLUSIONS

The diagnostic performance of leukocyte estearase by reactive strips was similar to the microscopy of leukocytes and bacteria but the nitrite test had a lower performance. The combination of the leukocytes and bacteriuria measured by hpf appears to be very useful in the diagnosis of UTI.

[Multisystemic impact in the full-term newborn with perinatal asphyxia]

We studied 30 full-term newborn infants, admitted to the newborn intensive care unit of "Manuel Gea González" General Hospital between January 1, 1989 and December 31, 1990. All infants had 5-minute Apgar score of 5 or less. The disturbances related to: brain, heart, liver, bowel, coagulation system, calcium and glucose homeostasis were investigate in all cases. Of the 30 infants, 29 (97%) had developed 1 to 7 abnormalities in the systems studied. Most of them had from 2 to 5 abnormalities (77%). The commonest disturbance was brain involvement in 22 cases (73%); metabolic and coagulation changes had also been observed, while heart disturbances were less common. There was no significant difference between the intensity and number of systemic abnormalities observed in these infants and the alterations seen during pregnancy, labor, delivery, administration of anesthesia and Apgar score. These observations suggest a striking relationship between asphyxia in the newborn infant and the development of systemic disturbances.