Summary
A prospective survey was carried out among 302 consecutive diabetic patients in three French diabetes centres to study the sensitivity and specificity of screening for microalbuminuria using the Clinitek® Microalbumin strip. Urine samples positive for proteinuria, haematuria, leukocyturia or nitrates using the Multistix® strip were excluded from the study. The results obtained with the Clinitek® Microalbumin strip were compared with those using the reference method of the biological laboratory of each centre on the same urine sample. A positive result was defined as an albumin creatinine ratio ³30 mg/g.
In the study population, 48 (17%) subjects were found to be positive for microalbuminuria according to the reference assay. However, the different centres produced different rates (25%, 11% and 15%). Using Clinitek® Microalbumin, a positive result was found in 86 patients (29%; 39%, 26% and 23%, respectively). There was good agreement in the population as a whole (81%, k = 0.47 ± 0.06). Sensitivity was 79%, specificity 81%, positive predictive value 46%, negative predictive value 95% and positive likelihood ratio 4.2.
The authors conclude that its excellent negative predictive value makes Clinitek® Microalbumin a good screening test for microalbuminuria. Positive results should be confirmed using a reference assay.

Comment
Microalbuminuria is a predictor of nephropathy and of increased cardiovascular morbidity and mortality in diabetic patients. Identification of diabetic patients with microalbuminuria is mandatory if they are to be offered optimal treatment with, for example, ACE inhibitors or angiotensin receptor blockers to reduce the risk of manifest renal disease and cardiovascular morbidity and mortality [1].
Screening for microalbuminuria is traditionally carried out using 24-h urine excretion. Because of the difficulty of obtaining a complete collection, the albumin creatinine ratio in a random urine sample has been validated and found useful for detecting the presence of microalbuminuria. An albumin creatinine ratio of 30 mg/g corresponds to a level of 30 mg albumin in a 24-h urine collection, equivalent to the detection level for microalbuminuria. The authors explain that screening for microalbuminuria is not commonly performed in France and that biological assays for determining albumin in urine are only available in specialized laboratories. The provision of tools to facilitate the screening process for microalbuminuria is clearly important.
The present evaluation of a simple, fast and convenient way of screening for microalbuminuria using Clinitek® Microalbumin demonstrates that the strip is useful in the absence of easy access to biological analysis for urinary albumin.
However, other screening methods such as the Micral-Test II®, based on semiquantitative strip assays, have been developed and proven useful in screening for microalbuminuria [2]. Unfortunately, Clinitek® Microalbumin has not been evaluated against the earlier Micral-Test II® strips.
Furthermore, the decision to use a strip for screening for microalbuminuria is dependent on the cost of the strip and the cost of analysing any positive samples using a biological assay.
Although the Clinitek® Microalbumin strip appears to be a useful tool for screening for microalbuminuria, further information is needed before it can be utilized in local diabetes clinics.

References
1. Parving H-H, Lehnert H, Brochner-Mortensen J et al. The effect of irbesartan on the development of diabetic nephropathy in patients with type 2 diabetes. N Engl J Med 2001; 345: 870–8.
2. Mogensen CE, Viberti GC, Peheim E et al. Multicenter evaluation of the Micral-Test II test strip, an immunologic rapid test for the detection of microalbuminuria. Diabetes Care 1997; 20: 1642–6.

Summary and Comment:
Elisabeth Mathiesen, Copenhagen, Denmark