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Qualitative Analysis of Abnormal Constituents of Urine

1. Aim

To screen a teaching urine specimen for selected abnormal constituents and document the limits of each qualitative result. The PCI syllabus lists this as the second Medicinal Biochemistry practical. A teaching result is not a diagnosis. [1, 2, 3]

2. Requirements

Use an instructor-approved control or deidentified specimen, labelled test tubes or validated test strips, appropriate controls, timer, gloves, coat, eye protection, and a result sheet. The college manual discusses protein, reducing sugar, ketone bodies, bile pigments, bile salts, and blood. It also includes a historical benzidine blood test. Because benzidine is a recognized carcinogen, do not use that test; choose a locally approved modern method for blood detection. Exact strip brand, reagent composition, volumes, timing, and decision thresholds must follow your college lab manual and instructor's method sheet. [2, 4]

3. Theory

Urinalysis may detect substances such as excess protein, glucose, ketones, bilirubin, and blood. Different tests answer different questions. Benedict's reaction detects reducing substances and does not specifically identify glucose. A glucose oxidase test is more specific for glucose. Protein tests may have interference from urine conditions, and a positive blood strip cannot by itself distinguish intact red cells from free hemoglobin or myoglobin. A single abnormal screen therefore requires confirmation and clinical context. [2, 3]

The manual includes several chemical tube tests. Some use strong acid, ammonia, or heat. For this article, the selected panel is performed only under a written current laboratory method, preferably with prepared controls. Record the method actually used rather than copying a historical procedure. If specimen identity, expiry of a reagent, or control result is unknown, the finding must be recorded here. The common language of positive and negative applies only to the chosen method's cutoff; it does not prove presence or absence at every concentration. [2, 3]

4. Procedure

1. Confirm the teaching specimen identity, collection and storage details, and whether the sample is a control. Missing information must be recorded here. [2, 3]
2. Select a locally approved panel for protein, glucose or reducing substances, ketones, bilirubin, and blood. Record which target each method actually detects. Do not use benzidine. [2, 4]
3. Check reagent or strip expiry, lot, controls, reading time, and specimen volume against the local procedure. Enter your college lab manual and instructor's method sheet for any unspecified value. [2]
4. Perform each authorized test on a separate aliquot or specified strip pad, following the current written method and its protective controls. [2, 3]
5. At the specified time, record the observed color, turbidity, or instrument reading in the observation column before writing an interpretation. [2]
6. Compare the response with both positive and negative controls. Mark a failed-control test invalid, even if the sample changed color. [2, 3]
7. Record any presumptive positive for instructor review and follow the instructor-approved confirmatory method. Dispose of specimen and chemical waste through local channels. [2, 3]

5. Calculation, graph, or images as appropriate

Worked record calculation: A five-target panel with one sample reading and two control readings for each target requires 5 × 3 = 15 entries. If one target lacks a valid control, only four targets can be interpreted, and that target's result must be recorded here. This arithmetic checks record completeness; it does not establish a clinical cutoff. [2]

6. Result

Report each target as presumptive positive, presumptive negative, indeterminate, or invalid, with the observed response and control status. Do not equate a reducing-substance result with confirmed glucose. Qualified review is required for clinical meaning; record the assigned confirmatory test from the approved method. [2, 3]

7. References

1. Pharmacy Council of India. Pharm.D. Regulations, 2008, Medicinal Biochemistry practical list.
2. East Point College of Pharmacy. Medicinal Biochemistry Practical Manual, abnormal urine constituent section.
3. National Library of Medicine, MedlinePlus. Urinalysis.
4. National Institute for Occupational Safety and Health. Benzidine. Documents the occupational hazard of the historical test reagent.

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Theory notes: Medicinal Biochemistry