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During the first wave of Covid-19 in France, in spring 2020, healthcare institution's laboratory had to adapt itself quickly to the growing demand for emergency biology, in particular by reorganizing their POCT analyzers: redeployment of analyzers and/or new installations. In order to analyze this management, a subgroup of 15 hospital biologists from the SFBC Working Group "Biochemical markers of Covid-19" sent, in fall 2020, an on-line survey to French hospital laboratories using POCT. Answers analysis (n = 86) shows a territorial disparity related to the severity of the first wave: increased activity essentially in red zones, management of unexpected situations, training of additional nursing staff for 40 % of the laboratories... The survey also showed simplification of aspects related to accreditation those periods of health crisis. An additional survey, carried out in the spring of 2021, showed good overall satisfaction of the healthcare services (n = 139) concerning the services provided by biology in the POCT sector. Because of their great adaptation capacity, the laboratories and their POCT-teams have played a key role in the management of the first wave of Covid-19 in France. However, the success of these organizations requires an essential collaboration between laboratories and healthcare services. The results of this survey are fundamental in the context of the prolongation of the pandemia throughout the world with a POCT sector appearing to be growing.

The fibrobalst growth factor 23 (FGF23) is a protein secreted in the plasma by bone cells. FGF23 controls phosphate and calcitriol plasma concentration. Its main physiological targets are the kidney and the parathyroid gland. Its production is stimulated by phosphate intake and plasma calcitriol levels. FGF23 binds a receptor at the cell surface that is composed by the association of a FGF receptor with the protein Klotho. Klotho expression is restricted to few organs including the kidney and the parathyroid gland. Klotho, which is expressed at the cell surface, can also be released in the plasma after an enzymatic cleavage. The role of the circulating form of Klotho is unknown. In addition to its role as a co-receptor Klotho may control the stability of the renal sodium phosphate transporter NPT2a and the calcium channel TRPV5 via enzymatic properties. FGF23 or Klotho gene disruption in mice leads to similar phenotypes except for the levels of FGF23, undetectable or increased respectively. FGF23 plasma concentration rises from the early stage of renal insufficiency to prevent plasma phosphate concentration from increasing. In parallel Klotho production seems to diminish. These modifications trigger the secondary hyperparathyroidism observed in renal insufficiency. The increase in FGF23 concentration and the decrease in Klotho levels are associated in animals and in human as well to an augmentation of mortality especially from cardiovascular causes and to heart modification: hypertrophy or dysfunction.

Since 2005, international guidelines propose a stadification for chronic renal failure based on the glomerular filtration rate (GFR) value. The performance of the creatinine-based equations allowing the estimation of GFR and the bias of the creatinine measurements is, more than ever, a crucial issue. The consequences for the clinical biologists are of importance. First, the Cockcroft-Gault formula must be replaced by the four variable-MDRD equation. Second, the biologists must chose from the "175" and the "186" versions of the MDRD equation. The first one fits the creatinine methods which are traceable to the reference method (liquid or gas chromatography coupled to mass spectrometry). The second equation must be used for creatinine methods, which are not traceable to the reference method. Today, only some enzymatic methods can prove that they are traceable to the reference method. For the colorimetric methods, future is inclear.

Cystatin C is a low molecular weight-protein, which may replace creatinine for the evaluation of renal function, particularly in the clinical settings where the relationship between creatinine production and muscular mass impairs the clinical performance of creatinine. This paper intends to summarize the current knowledge about the physiology of cystatin C and about its use as a renal marker, alone or within formulas developed to estimate the glomerular filtration rate. Moreover, this paper reviews the recent data about potential other applications of cystatin C, especially in cardiology, in oncology and in clinical pharmacology.